Extending the MR-Egger method for multivariable Mendelian randomization to correct for both measured and unmeasured pleiotropy

Causal Mediation Analysis: A Summary-Data Mendelian Randomization Approach

Summary-data Mendelian randomization (MR), a widely used approach in causal inference, has recently attracted attention for improving causal mediation analysis. Two existing methods corresponding to the difference method and product method of linear mediation analysis have been developed to perform MR-based mediation analysis using the inverse-variance weighted method (MR-IVW). Despite these developments, there is still a need for more rigorous, efficient, and precise MR-based mediation methodologies. In this study, we develop summary-data MR-based frameworks for causal mediation analysis. We improve the accuracy, statistical efficiency and robustness of the existing MR-based mediation analysis by implementing novel variance estimators for the mediation effects, deriving rigorous procedures for statistical inference, and accounting for widespread pleiotropic effects. Specifically, we propose Diff-IVW and Prod-IVW to improve upon the existing methods and provide the pleiotropy-robust methods (Diff-Egger, Diff-Median, Prod-Egger, and Prod-Median), adapted from MR-Egger and MR-Median, to enhance the robustness of the MR-based mediation analysis. We conduct comprehensive simulation studies to compare the existing and proposed methods. The results show that the proposed methods, Diff-IVW and Prod-IVW, improve statistical efficiency and type I error control over the existing approaches. Although all IVW-based methods suffer from directional pleiotropy biases, the median-based methods (Diff-Median and Prod-Median) can mitigate such biases. The differences among the methods can lead to discrepant statistical conclusions as demonstrated in real data applications. Based on our simulation results, we recommend the three proposed methods in practice: Diff-IVW, Prod-IVW, and Prod-Median, which are complementary under various scenarios.

Triangulated evidence provides no support for bidirectional causal pathways between diet/physical activity and depression/anxiety

BACKGROUND

Previous studies (various designs) present contradicting insights on the potential causal effects of diet/physical activity on depression/anxiety (and vice versa). To clarify this, we employed a triangulation framework including three methods with unique strengths/limitations/potential biases to examine possible bidirectional causal effects of diet/physical activity on depression/anxiety.

METHODS

Study 1: 3-wave longitudinal study (n = 9,276 Dutch University students). Using random intercept cross-lagged panel models to study temporal associations. Study 2: cross-sectional study (n = 341 monozygotic and n = 415 dizygotic Australian adult twin pairs). Using a co-twin control design to separate genetic/environmental confounding. Study 3: Mendelian randomization utilizing data (European ancestry) from genome-wide association studies (n varied between 17,310 and 447,401). Using genetic variants as instrumental variables to study causal inference.

RESULTS

Study 1 did not provide support for bidirectional causal effects between diet/physical activity and symptoms of depression/anxiety. Study 2 did provide support for causal effects between fruit/vegetable intake and symptoms of depression/anxiety, mixed support for causal effects between physical activity and symptoms of depression/anxiety, and no support for causal effects between sweet/savoury snack intake and symptoms of depression/anxiety. Study 3 provides support for a causal effect from increased fruit intake to the increased likelihood of anxiety. No support was found for other pathways. Adjusting the analyses including diet for physical activity (and vice versa) did not change the conclusions in any study.

CONCLUSIONS

Triangulating the evidence across the studies did not provide compelling support for causal effects of diet/physical activity on depression/anxiety or vice versa.

Multi-INTACT: integrative analysis of the genome, transcriptome, and proteome identifies causal mechanisms of complex traits

We present multi-integration of transcriptome-wide association studies and colocalization (Multi-INTACT), an algorithm that models multiple "gene products" (e.g., encoded RNA transcript and protein levels) to implicate causal genes and relevant gene products. In simulations, Multi-INTACT achieves higher power than existing methods, maintains calibrated false discovery rates, and detects the true causal gene product(s). We apply Multi-INTACT to GWAS on 1408 metabolites, integrating the GTEx expression and UK Biobank protein QTL datasets. Multi-INTACT infers 52 to 109% more metabolite causal genes than protein-alone or expression-alone analyses and indicates both gene products are relevant for most gene nominations.

Genetically Supported Causality Between Micronutrients and Sleep Behaviors: A Two-Sample Mendelian Randomization Study

BACKGROUND

Sleep behaviors, defined by the total duration of sleep and chronotype, significantly influence overall health. Compromised sleep quality, which is often manifested through reduced sleep duration and the prevalence of insomnia, has been found to be associated with micronutrient deficiencies. Nonetheless, the existence of a causal relationship between micronutrient levels and sleep behaviors remains to be established.

METHODS

A two-sample Mendelian randomization (MR) analysis, utilizing data from genome-wide association studies (GWAS), was employed to examine the associations between 15 micronutrients (copper; calcium; carotene; folate; iron; magnesium; potassium; selenium; vitamins A, B12, B6, C, D, and E; and zinc) and various sleep behaviors, including short and long sleep durations, insomnia, and chronotype. Furthermore, multivariable MR (MVMR) analysis was performed to address potential confounding due to the interrelationships among micronutrients and to discern potential causal relationships.

RESULTS

The MR analysis identified a causal association between folate levels and chronotype (odds ratio [OR] = 1.09; 95% confidence interval [CI]: 1.01-1.17; p = 0.02), indicating a tendency toward morningness. Conversely, vitamin B6 (OR = 0.91; 95% CI: 0.86-0.96; p = 1.05 × 10-3) and vitamin D (OR = 0.94; 95% CI: 0.88-1.00; p = 0.03) showed inverse associations with chronotype, indicative of a preference for eveningness. MVMR analysis confirmed the positive association between folate (OR = 1.286, 95% CI = 1.124-1.472, p < 0.001) and chronotype and a negative association with vitamin B6 (OR = 0.750, 95% CI = 0.648-0.868, p < 0.001). No causal relationships were established between micronutrient levels and either sleep duration or insomnia.

CONCLUSIONS

Elevated folate levels correlate with morning-type preferences ("morning birds"), while higher concentrations of vitamin B6 are associated with evening-type preferences ("evening owls").

Relationship of urate-lowering drugs with cognition and dementia: A Mendelian randomization and observational study

Prior studies have presented paradoxical results regarding the association of uric acid-lowering drugs (ULDs) therapy with cognition and dementia. We aimed to explore this correlation. In this observational study, we extracted and analyzed the data from the National Health and Nutrition Examination Survey (NHANES) database and the FDA Adverse Event Reporting System (FAERS) database to investigate the association of ULDs with cognitive function and dementia. Two-simple Mendelian randomization (MR) and multivariable MR (MVMR) analyses were conducted to evaluate the causal associations of ULDs for all common types of dementia, including Alzheimer's disease (AD), vascular dementia (VD), frontotemporal dementia (FTD), and dementia with Lewy bodies (DLB). In the NHANES database, regardless of whether ULDs were included only or adjusted for covariates, the linear regression models did not find a correlation between ULDs and three cognitive tests (all p > 0.05). In the FAERS database, the dementia signal in ULDs lost significance after stepwise constraints (the lower limit of proportional reporting ratio lower than 1). In the two-sample MR analysis, allopurinol was associated with an increased risk of VD (OR = 123.747, p = 0.002), and a positive causal relationship was found between uricosuric drugs and AD (OR = 1.003, p = 0.003). However, the significance disappeared after adjusting for risk factors of dementia (p > 0.05). This study indicates that ULDs may not be related to an increase or decrease risk of cognition function and dementia, including all common types of dementia (AD, VD, FTD, and DLB).

Causal association between insulin sensitivity index and Alzheimer's disease

Evidence from observational and Mendelian randomization (MR) studies suggested that insulin resistance (IR) was associated with Alzheimer's disease (AD). However, the causal effects of different indicators of IR on AD remain inconsistent. Here, we aim to assess the causal association between the insulin sensitivity index (ISI), a measure of post-prandial IR, and the risk of AD. We first conducted primary and secondary univariable MR analyses. We selected 8 independent genome-wide significant (p < 5E-08, primary analyses) and 61 suggestive (p < 1E-05, secondary analyses) ISI genetic variants from large-scale genome-wide association studies (GWAS; N = 53 657), respectively, and extracted their corresponding GWAS summary statistics from AD GWAS, including IGAP2019 (N = 63 926) and FinnGen_G6_AD_WIDE (N = 412 181). We selected five univariable MR methods and used heterogeneity, horizontal pleiotropy test, and leave-one-out sensitivity analysis to confirm the stability of MR estimates. Finally, we conducted a meta-analysis to combine MR estimates from two non-overlapping AD GWAS datasets. We further performed multivariable MR (MVMR) to assess the potential mediating role of type 2 diabetes (T2D) on the association between ISI and AD using two MVMR methods. In univariable MR, utilizing 8 genetic variants in primary analyses, we found a significant causal association of genetically increased ISI with decreased risk of AD (OR = 0.79, 95% CI: 0.68-0.92, p = 0.003). Utilizing 61 genetic variants in secondary analyses, we found consistent findings of a causal effect of genetically increased ISI on the decreased risk of AD (OR = 0.89, 95% CI: 0.82-0.96, p = 0.003). Heterogeneity, horizontal pleiotropy test, and leave-one-out sensitivity analysis ensured the reliability of the MR estimates. In MVMR, we found no causal relationship between ISI and AD after adjusting for T2D (p > 0.05). We provide genetic evidence that increased ISI is significantly and causally associated with reduced risk of AD, which is mediated by T2D. These findings may inform prevention strategies directed toward IR-associated T2D and AD.

Biological pathways underlying the relationship between childhood maltreatment and Multimorbidity: A Two-Step, multivariable Mendelian randomisation study

Childhood maltreatment has been associated with multimorbidity of depression, coronary artery disease and type 2 diabetes. However, the biological mechanisms underlying this association remain unclear. We employed two-step and multivariable Mendelian randomisation (MR) to understand the role of three potential biological mediating mechanisms - inflammation (92 proteins), metabolic processes (54 markers), and cortisol - in the link between childhood maltreatment liability and multimorbidity. Using summary statistics from large-scale genome-wide association studies of European ancestry for childhood maltreatment (N = 185,414) and multimorbidity (Neffective = 156,717), we tested for the presence of an indirect effect via each mediator individually. We found a potential role of metabolic pathways. Up to 11 % of the effect of childhood maltreatment on multimorbidity was mediated by triglycerides (indirect effect [95 %CI]: 0.018 [0.009-0.027]), 8 % by glycated haemoglobin (indirect effect: 0.013 [0.003-0.023]), and up to 7 % by high-density lipoprotein cholesterol (indirect effect: 0.011 [0.005-0.017]). We did not find evidence for mediation via any inflammatory protein or cortisol. Our findings shed light on the biological mechanisms linking childhood maltreatment liability to multimorbidity, highlighting the role of metabolic pathways. Future studies may explore underlying pathways via non-biological mediators (e.g., lifestyle factors) or via multiple mediators simultaneously.

Assessment of relationships between epigenetic age acceleration and multiple sclerosis: a bidirectional mendelian randomization study

BACKGROUND

The DNA methylation-based epigenetic clocks are increasingly recognized for their precision in predicting aging and its health implications. Although prior research has identified connections between accelerated epigenetic aging and multiple sclerosis, the chronological and causative aspects of these relationships are yet to be elucidated. Our research seeks to clarify these potential causal links through a bidirectional Mendelian randomization study.

METHODS

This analysis employed statistics approaches from genome-wide association studies related to various epigenetic clocks (GrimAge, HannumAge, PhenoAge, and HorvathAge) and multiple sclerosis, utilizing robust instrumental variables from the Edinburgh DataShare (n = 34,710) and the International Multiple Sclerosis Genetics Consortium (including 24,091 controls and 14,498 cases). We applied the inverse-variance weighted approach as our main method for Mendelian randomization, with additional sensitivity analyses to explore underlying heterogeneity and pleiotropy.

RESULTS

Using summary-based Mendelian randomization, we found that HannumAge was associated with multiple sclerosis (OR = 1.071, 95%CI:1.006-1.140, p = 0.033, by inverse-variance weighted). The results suggest that an increase in epigenetic age acceleration of HannumAge promotes the risk of multiple sclerosis. In reverse Mendelian randomization analysis, no evidence of a clear causal association of multiple sclerosis on epigenetic age acceleration was identified.

CONCLUSIONS

Our Mendelian randomization analysis revealed that epigenetic age acceleration of HannumAge was causally associated with multiple sclerosis, and provided novel insights for further mechanistic and clinical studies of epigenetic age acceleration-mediated multiple sclerosis.

The role of inflammatory factors in mediating the causal effects of type 1 diabetes mellitus on idiopathic pulmonary fibrosis: A two-step Mendelian randomization study

While recent studies suggested a potential causal link between type 1 diabetes mellitus (T1DM) but not type 2 diabetes mellitus (T2DM) and idiopathic pulmonary fibrosis (IPF), the involved mechanism remains unclear. Here, using a Mendelian randomization (MR) approach, we verified the causal relationship between the two types of diabetes mellitus and IPF and investigated the possible role of inflammation in the association between diabetes mellitus and IPF. Based on genome-wide association study (GWAS) summary data of T1DM, T2DM, and IPF, the univariable MR, multivariable MR (MVMR), and mediation MR were successively used to analyze the causal relationship. Inverse variance weighted was used as the main method to infer the causal effect, together with a series of sensitivity analyses. The univariable MR showed that only T1DM increased the risk of IPF, and there was no significant causal relationship between T2DM and IPF. The MVMR further verified that there was an independent direct causal effect of T1DM on IPF. Further mediation analysis showed that this effect was partly mediated by increasing C-X-C motif chemokine ligand 10 (CXCL10) and interleukin-12 subunit beta (IL-12B). In conclusion, T1DM is related to an increased risk of IPF. Notably, the causal effect was partially mediated by CXCL10 and IL-12B. Hence, monitoring T1DM patients may help in the early detection and prevention of IPF.

Causal linkage of psoriasis with ageing: Mendelian randomization and enrichment analysis towards telomere length and psoriasis

OBJECTIVE

Several studies demonstrated potential associations between the telomere length (TL) in leukocytes and psoriasis or psoriatic arthritis (PsA). This study aimed to investigate whether there was the causal genetic relationship between TL and psoriatic diseases bidirectionally.

METHODS

Two-sample univariable MR (UVMR) analysis was applied to explore the bidirectional causal association of TL with overall psoriasis, psoriasis vulgaris (PV) and PsA. Multivariable MR (MVMR) and the mediation effects analysis were applied to test whether the bidirectional associations between TLs and psoriasis were mediated by body mass index (BMI), alcohol, and smoking status.

RESULTS

According to the UVMR results, a negative causal impact of TL on the risk of overall psoriasis was found (OR = 0.775; 95% CI: 0.646-0.931; P = 6.36 × 10-3), and a similar trend was observed in the reversed direction for psoriasis-TL (IVW-β = -0.0097; 95% CI: -0.0170 to -0.0024; P = 9.12 × 10-3). There were also negative genetic associations between TL and PV bidirectionally. The independent association of genetically predicted TL and overall psoriasis persisted in the MVMR results controlled for BMI, smoking, and alcohol consumption (ORMVMR = 0.736; 95% CI: 0.597 to 0.907; P = 0.004). An independent significant association of genetic predisposition to PsA with TL was also found (βMVMR = 0.006; 95% CI: 0.001 to 0.012; P = 0.033). The mediation analysis showed that BMI partially mediated the reverse association between PSO and TL.

CONCLUSION

This MR study revealed an association between genetic indicators of shortened TL and risk of overall psoriasis and PV, and genetic predisposition to PsA was associated with longer TL. Key message What is already known on this topic?  Telomere length (TL) is acknowledged to reflect an individual's biological age but is also associated with dysregulated immune function and immunosenescence. The impact of aging on psoriasis is controversial. Existing evidence suggests that aging may influence pathological changes and clinical course but whether aging is an independent risk factor remains unclear. What this study adds?  The current study found an association between genetic indicators of shortened TL and the risk of overall psoriasis and psoriasis vulgaris (PV). There was a bidirectional link between genetically indicated overall psoriasis and shortened TL. A possible positive genetic association between PsA and TL was also found. How this study might affect research, practice, or policy?  Our study may provide evidence for TL as new diagnostic and therapeutic strategies in clinical practices for psoriasis. Greater efforts to psoriasis management may substantially reduce the aging attributable to TL shortening. Future large-scale GWAS and experimental studies are warranted to examine the mechanistic basis for links between TL and psoriasis to improve understanding and illuminate possible therapeutic targets for psoriatic disease.

Genetic prediction of blood metabolites mediating the relationship between gut microbiota and postpartum depression: A mendelian randomization study

BACKGROUND

Observational studies have suggested an association between gut microbiota(GM) and postpartum depression (PPD). However, the causal relationship remains unclear, and the role of blood metabolites in this association remains elusive.

METHODS

This study firstly elucidated the causal relationship among 196 GM taxa, 224 blood metabolites, and PPD from a genetic perspective, employing two-sample Mendelian randomization (MR). Subsequently, a two-step mediation MR approach was employed to explore the role of blood metabolites as potential mediators. To validate the relevant findings, we further selected other data (GM and blood metabolites) from the IEU Open GWAS and GWAS Catalog for analysis. Our primary analysis utilized the inverse variance weighted method. To enhance the robustness of our results, we also applied MR-Egger method, weighted median method, Cochran's Q test, MR-Egger regression, and MR-PRESSO.

RESULTS

MR analysis results revealed a nominal association (p < 0.05) between 13 GM taxa, 6 blood metabolites, and PPD. After multiple-testing correction (PFDR < 0.1), Bifidobacteriales (PFDR = 0.034), Bifidobacteriaceae (PFDR = 0.055) and Guanosine (PFDR = 0.081) showed significant causal relationships with PPD. In our validation results, the higher level of Alphaproteobacteria (OR: 1.057, 95% CI: 1.024-1.091; p = 0.0006) retained a causal relationship with a higher risk of PPD. Finally, mediation analysis revealed that the impact of Odoribacter on PPD was mediated indirectly through Hyodeoxycholate, with a mediation proportion of 16.8%.

CONCLUSION

Our findings elucidated the underlying mechanisms between the GM, blood metabolites, and PPD. These findings contribute to the prevention and diagnosis of PPD, offering novel insights into microbiome-based therapies and metabolite-targeted interventions for the treatment of PPD.

Exploring autism spectrum disorder and co-occurring trait associations to elucidate multivariate genetic mechanisms and insights

BACKGROUND

Autism spectrum disorder (ASD) is a partially heritable neurodevelopmental trait, and people with ASD may also have other co-occurring trait such as ADHD, anxiety disorders, depression, mental health issues, learning difficulty, physical health traits and communication challenges. The concomitant development of ASD and other neurological traits is assumed to result from a complex interplay between genetics and the environment. However, only a limited number of studies have performed multivariate genome-wide association studies (GWAS) for ASD.

METHODS

We conducted to-date the largest multivariate GWAS on ASD and 8 ASD co-occurring traits (ADHD, ADHD childhood, anxiety stress (ASDR), bipolar (BIP), disruptive behaviour (DBD), educational attainment (EA), major depression, and schizophrenia (SCZ)) using summary statistics from leading studies. Multivariate associations and central traits were further identified. Subsequently, colocalization and Mendelian randomization (MR) analysis were performed on the associations identified with the central traits containing ASD. To further validate our findings, pathway and quantified trait loci (QTL) resources as well as independent datasets consisting of 112 (45 probands) whole genome sequence data from the GEMMA project were utilized.

RESULTS

Multivariate GWAS resulted in 637 significant associations (p < 5e-8), among which 322 are reported for the first time for any trait. 37 SNPs were identified to contain ASD and one or more traits in their central trait set, including variants mapped to known SFARI ASD genes MAPT, CADPS and NEGR1 as well as novel ASD genes KANSL1, NSF and NTM, associated with immune response, synaptic transmission, and neurite growth respectively. Mendelian randomization analyses found that genetic liability for ADHD childhood, ASRD and DBT has causal effects on the risk of ASD while genetic liability for ASD has causal effects on the risk of ADHD, ADHD childhood, BIP, WA, MDD and SCZ. Frequency differences of SNPs found in NTM and CADPS genes, respectively associated with neurite growth and neural/endocrine calcium regulation, were found between GEMMA ASD probands and controls. Pathway, QTL and cell type enrichment implicated microbiome, enteric inflammation, and central nervous system enrichments.

CONCLUSIONS

Our study, combining multivariate GWAS with systematic decomposition, identified novel genetic associations related to ASD and ASD co-occurring driver traits. Statistical tests were applied to discern evidence for shared and interpretable liability between ASD and co-occurring traits. These findings expand upon the current understanding of the complex genetics regulating ASD and reveal insights of neuronal brain disruptions potentially driving development and manifestation.

Potential Causal Association Between Atrial Fibrillation/Flutter and Primary Open-Angle Glaucoma: A Two-Sample Mendelian Randomisation Study

Background: A few studies have reported controversial relationships between atrial fibrillation/flutter (AF/L) and primary open-angle glaucoma (POAG). This study aimed to investigate the potential causal relationship between AF/L and POAG. Methods: Single-nucleotide polymorphisms associated with exposure to AF/L were selected as instrumental variables with significance (p < 5.0 × 10-8) from a genome-wide association study (GWAS) by FinnGen. The GWAS summary of POAG from the UK Biobank was used as the outcome dataset. A two-sample Mendelian randomisation (MR) study was performed to assess the causal effects of AF/L on POAG. In addition, potential confounders, including hypertension, autoimmune hyperthyroidism, sleep apnoea, and alcohol use disorder, were assessed using multivariable MR analysis. Results: There was a significant causal association of AF/L with POAG (odds ratio [OR] = 1.26, 95% confidence interval [CI] = 1.07-1.48, p = 0.005 using inverse-variance weighting [IVW]). Multivariable MR analysis confirmed a causal association of AF/L with POAG (OR = 1.24, 95% CI = 1.02-1.51, p = 0.034 using IVW), but hypertension, hyperthyroidism, sleep apnoea and alcohol use disorder did not show significant causal associations with POAG (all p > 0.05). Conclusions: This established causal relationship between AF/L and POAG supports the need for further investigation into the role of AF/L as a possible risk factor for POAG. Further research is required to confirm these findings.

The Potential Causal Association of Apolipoprotein A and B and Age-Related Macular Degeneration: A Mendelian Randomisation Study

BACKGROUND/OBJECTIVES

Research has suggested a potential relationship between apolipoproteins A (ApoA) and B (ApoB) and age-related macular degeneration (AMD). This study explored the potential causal relationship between ApoA/ApoB levels and AMD/AMD subtypes using two-sample Mendelian randomisation (MR).

METHODS

We selected 308 single nucleotide polymorphisms (SNPs) for ApoA and 198 SNPs for ApoB from the UK Biobank data. Summary statistics for AMD were collected from the genome-wide association study of the FinnGen project. We performed two-sample MR to assess the causal effects of ApoA/ApoB on AMD and its subtypes. Potential confounders, including body mass index, C-reactive protein level, and smoking status, were assessed using a multivariable MR analysis.

RESULTS

ApoA showed a significant causal association with AMD (odds ratio [OR] = 1.14, 95% confidence interval [CI] = 1.05-1.25, p = 0.003) and was linked to both dry (p = 0.004) and wet (p = 0.025) AMD. ApoB showed a decreasing trend in dry AMD risk (p = 0.074), though not significant, and was not associated with overall or wet AMD. The multivariable MR analysis showed no significant association of ApoA with any AMD subtype (p > 0.05). ApoB decreased dry AMD risk (OR = 0.89, 95% CI = 0.80-0.99, p = 0.039), with trends for overall and wet AMD that were not significant (p = 0.070 and p = 0.091, respectively).

CONCLUSIONS

These findings suggest that ApoB is associated with lower AMD risk, particularly for dry AMD. Further research is needed to clarify lipid biomarker's role as AMD risk factors.

Role of blood lipids in mediating the effect of dietary factors on gastroesophageal reflux disease: a two-step mendelian randomization study

BACKGROUND

Growing studies have indicated an association between dietary factors and gastroesophageal reflux disease (GERD). However, whether these associations refer to a causal relationship and the potential mechanism by which dietary factors affect GERD is still unclear.

METHODS

A two-step mendelian randomization analysis was performed to obtain causal estimates of dietary factors, blood lipids on GERD. Independent genetic variants associated with 13 kinds of dietary factors and 5 kinds of blood lipids at the genome-wide significance level were selected as instrumental variables. The summary statistics for GERD were obtained from European Bioinformatics Institute, including 129,080 cases and 473,524 controls. Inverse variance weighted was utilized as the main statistical method. MR-Egger intercept test, Cochran's Q test, and leave-one-out analysis were performed to evaluate possible heterogeneity and pleiotropy. And the potential reverse causality was assessed using Steiger filtering.

RESULTS

The results of the inverse variance weighted method indicated that genetically predicted total pork intake (OR = 2.60, 95% CI: 1.21-5.58, p = 0.0143), total bread intake (OR = 0.68, 95% CI: 0.46-0.99, p = 0.0497), total cereal intake (OR = 0.42, 95% CI: 0.31-0.56, p = 2.98E-06), and total cheese intake (OR = 0.41, 95% CI: 0.27-0.61, p = 1.06E-05) were associated with the risk of GERD. Multivariable Mendelian randomization analysis also revealed a negative association between total cereal intake, total cheese intake and the risk of GERD, but the effect of total pork intake and total bread intake on GERD disappeared after adjustment of smoking, alcohol consumption, use of calcium channel blockers, BMI, physical activity levels, and biological sex (age adjusted). Furthermore, the concentration of low-density lipoprotein cholesterol (LDL-C) is negatively correlated with total cheese intake, which mediates the impact of total cheese intake on GERD. The proportion mediated by LDL-C is 2.27% (95%CI: 1.57%, 4.09%).

CONCLUSIONS

This study provides evidence that an increase in total cereal intake and total cheese intake will decrease the risk of GERD. Additionally, LDL-C mediates the causal effect of total cheese intake on GERD. These results provide new insights into the role of dietary factors and blood lipids in GERD, which is beneficial for disease prevention.

Insulin-related traits and prostate cancer: A Mendelian randomization study

Investigating the causal relationship between insulin secretion and prostate cancer (PCa) development is challenging due to the multifactorial nature of PCa, which complicates the isolation of the specific impact of insulin-related factors. We conducted a Mendelian randomization (MR) study to investigate the associations between insulin secretion-related traits and PCa. We used 36, 60, 56, 23, 48, and 49 single nucleotide polymorphisms (SNPs) as instrumental variables for fasting insulin, insulin sensitivity, proinsulin, and proinsulin in nondiabetic individuals, individuals with diabetes, and individuals receiving exogenous insulin, respectively. These SNPs were selected from various genome-wide association studies. To clarify the causal relationship between insulin-related traits and PCa, we utilized a multivariable MR analysis to adjust for obesity and body fat percentage. Additionally, two-step Mendelian randomization was conducted to assess the role of insulin-like growth factor 1 (IGF-1) in the relationship between proinsulin and PCa. Two-sample MR analysis revealed strong associations between genetically predicted fasting insulin, insulin sensitivity, proinsulin, and proinsulin in nondiabetic individuals and the development of PCa. After adjustment for obesity and body fat percentage using multivariable MR analysis, proinsulin remained significantly associated with PCa, whereas other factors were not. Furthermore, two-step MR analysis demonstrated that proinsulin acts as a negative factor in prostate carcinogenesis, largely independent of IGF-1. This study provides evidence suggesting that proinsulin may act as a negative factor contributing to the development of PCa. Novel therapies targeting proinsulin may have potential benefits for PCa patients, potentially reducing the need for unnecessary surgical treatments.

Estimating and visualising multivariable Mendelian randomization analyses within a radial framework

BACKGROUND

Mendelian randomization (MR) is a statistical approach using genetic variants as instrumental variables to estimate causal effects of a single exposure on an outcome. Multivariable MR (MVMR) extends this to estimate the direct effect of multiple exposures simulatiously. MR and MVMR can be biased by the presence of pleiotropic genetic variants in the set used as instrumental variables, violating one of the core IV assumptions. Genetic variants that give outlying estimates are often considered to be potentially pleiotropic variants. Radial plots can be used in MR to help identify these variants. Analogous plots for MVMR have so far been unavailable due to the multidimensional nature of the analysis.

METHODS

We propose a radial formulation of MVMR, and an adapted Galbraith radial plot, which allows for the estimated effect of each exposure within an MVMR analysis to be visualised. Radial MVMR additionally includes an option for removal of outlying SNPs which may violate one or more assumptions of MVMR. A RMVMR R package is presented as accompanying software for implementing the methods described.

RESULTS

We demonstrate the effectiveness of the radial MVMR approach through simulations and applied analyses. We highlight how outliers with respect to all exposures can be visualised and removed through Radial MVMR. We present simulations that illustrate how outlier removal decreases the bias in estimated effects under various forms of pleiotropy. We apply Radial MVMR to estimate the effect of lipid fractions on coronary heart disease (CHD). In combination with simulated examples, we highlight how important features of MVMR analyses can be explored using a range of tools incorporated within the RMVMR R package.

CONCLUSIONS

Radial MVMR effectively visualises causal effect estimates, and provides valuable diagnostic information with respect to the underlying assumptions of MVMR.

Unveiling therapeutic targets for spinal stenosis from genetic insights: a Mendelian randomization analysis

Spinal stenosis is a commonly chronic spinal degenerative disease, which is a major cause of pain and dysfunction in the elderly. Mendelian randomization (MR) has been widely applied to repurpose licensed drugs and identify novel therapeutic targets. Consequently, we intended to identify new therapeutic targets for spinal stenosis and to analyze their possible mechanisms and potential side effects.We conducted the Mendelian randomization analysis to identify potential drug targets for the management of spinal stenosis. Cis-expressed quantitative trait loci (cis-eQTL) data as genetic instrumental variables were acquired from the eQTLGen consortium. The summary statistics for single nucleotide polymorphism (SNP) associations of spinal stenosis were obtained from the FinnGen study(20,807 cases and 294,770 controls). Co-localization analysis was performed to determine whether there was shared causal variation between the SNPs associated with spinal stenosis as well as the eQTL. Multiple external validations were performed to reinforce the reliability and stability of the findings utilizing the cis-eQTL from the GTEx portal, the Ferkingstad et al. pQTL dataset, and the Sun et al. pQTL dataset. The viability of the identified drug targets for future clinical applications was elucidated through the phenome-wide association study and drug candidate prediction. Three drug targets (BMP6, DLK1, and GFPT1) exhibited significant causal associations with spinal stenosis in the eQTLGen cohort by MR analysis, which was strongly supported by the results of the co-localization analysis. The causal association of DLK1 and GFPT1 with spinal stenosis remained remarkable with multiple external validations. Multivariate MR and phenome-wide association study analysis indicated that both targets were not associated with other traits. In addition, phenome-wide association study analysis and drug prediction analysis demonstrated the potential of these two targets for future clinical applications. In this study, DLK1 and GFPT1 were identified as promising novel therapeutic targets for spinal stenosis, providing initial genetic insights for drug development in spinal stenosis.

Causal relationships between uremic metabolites or toxins and heart failure: Univariate and multivariate Mendelian randomization

Studies have shown that uremia, renal failure and heart failure (HF) are closely related. However, whether this association reflects a causal effect is still unclear. The aim of this study was to evaluate the causal effect of uremic metabolites or toxins on HF. Mendelian randomization (MR) analysis was conducted to evaluate the causal effect of 11 uremia-related metabolites on HF risk using single-nucleotide polymorphisms (SNPs) from a genome-wide association study. A protein-protein interaction network was constructed to study the function of SNPs corresponding to HF-related factors. Univariate and multivariate MR analyses demonstrated that lipoprotein A and apolipoprotein B were positively correlated with HF. The SNPs corresponding to these key factors were related mainly to MAP kinase activity and lipid metabolic processes. Overall, we identified 2 uremia-related exposure factors (lipoprotein A and apolipoprotein B) closely related to HF, laying a theoretical foundation for the treatment of HF with renal failure or uremia.

The association between fruit and vegetable intake and gastrointestinal cancers risk from Mendelian randomization analysis

Recent research has demonstrated a relationship between fruit and vegetable intake and gastrointestinal cancers, but the causality of these associations remains uncertain. This investigation sought to elucidate whether there is a potential causal relationship between the intake of fruits and vegetables and the risk of gastrointestinal cancers. Employing two-sample Mendelian randomization (MR), this research explored the causative influence of consuming fruits (fresh and dried) and vegetables (salads/raw and cooked) on the susceptibility to gastrointestinal cancers. The UK Medical Research Council-Integrative Epidemiology Unit (MRC-IEU) provided the summary statistics for these exposure variables, while the summary statistics for outcome data came from four other data sources. Univariable and multivariable MR were performed using inverse variance-weighted (IVW), MR-Egger, weighted media (WM), and Lasso model methods. Besides, multiple methods were employed for sensitivity analyses to guarantee the robustness of the findings, including MR-Egger intercept, Cochran's Q test, and MR-PRESSO. Furthermore, the Phenoscanner V2 database was employed to identify possible confounders. The main analysis of univariable MR found that dried fruit consumption provided protection against pancreatic and oral cavity/pharyngeal cancers. However, this correlation becomes non-significant when potential confounders such as smoking, drinking, and body mass index (BMI) are accounted for. Furthermore, neither univariate nor multivariate MR analyses revealed enough data to prove a causal relationship between the intake of fresh fruit, vegetables (including salad/raw and cooked), and gastrointestinal cancers. There is insufficient evidence for a causal association between the consumption of fruits and vegetables and the occurrence of gastrointestinal cancers. Further empirical research is needed to corroborate these dietary factors' role in the etiology of gastrointestinal cancers.

Causal relationship between cancer and immune cell traits: A two-sample mendelian randomization study

Background

Observational studies provide evidence of correlations between cancer and the immune system. Previous research has established associations between immune traits and the propensity for developing certain cancers. However, a systematic exploration of these connections remains largely uncharted. Therefore, further investigation is needed to examine the causal association between cancer and immune cell traits using Mendelian randomization (MR) approach.

Methods

We identified genetic instruments for breast cancer (BC), lung cancer (LC), endometrial cancer (EC), ovarian cancer (OC), prostate cancer (PC), and their subtype cancers to investigate their potential causal impact on immune traits. Data on cancer and immune cell traits were obtained from the IEU Open GWAS project. To assess whether these five cancer types and subtype cancers have a causal association with immune cell traits, we conducted two-sample MR analyses. Additionally, we conducted bidirectional MR analyses to examine the direction of causal relationships and adjusted for potentially related pleiotropy through multivariable MR analysis.

Results

We have identified several causal relationships between different types of cancer and immune traits. We found that breast cancer may influence 49 immune cell traits, endometrial cancer may influence 38, lung cancer may influence 25, ovarian cancer may influence 19, and prostate cancer may influence 28. Among these, breast cancer and lung cancer were associated with four common immune traits: CD25 on IgD- CD38dim, CD25 on sw mem, CD24 on IgD- CD38-, and CD25 on IgD- CD38-. Lung cancer and prostate cancer shared four immune traits: CD25 on IgD+ CD24+, CD25 on IgD+ CD38-, CD66b on CD66b++ myeloid cell, DN (CD4-CD8-) AC. Endometrial cancer and ovarian cancer shared two immune traits: TD DN (CD4-CD8-) %DN, EM DN (CD4-CD8-) %DN. Breast cancer and endometrial cancer shared one immune trait: CD20 on IgD- CD38dim. Endometrial cancer and prostate cancer shared one immune trait: CCR2 on myeloid DC. Lastly, breast cancer, lung cancer, and prostate cancer shared one immune trait: CD25 on CD24+ CD27+. Additionally, we identified specific immune traits that may serve as protective or risk factors for cancers. We found 14 immune traits may influence breast cancer, 9 immune traits may influence endometrial cancer, 22 immune traits may influence lung cancer, 9 immune traits may influence ovarian cancer, and 14 immune traits may influence prostate cancer. Among these, breast cancer and prostate cancer shared three immune traits: HLA DR++ monocyte %monocyte, HLA DR on plasmacytoid DC, and HLA DR on DC. Lung cancer and ovarian cancer shared one immune trait: CD62L- monocyte %monocyte. Prostate cancer and endometrial cancer shared one immune trait: HLA DR on CD33dim HLA DR + CD11b+. Lastly, ovarian cancer and prostate cancer shared one immune trait: CD3 on resting Treg.

Conclusions

Our MR study suggests a potential relationship between immune traits and cancers, particularly highlighting 14 immune traits that are simultaneously influenced by two or three of five cancer types, while also indicating that 6 immune traits may simultaneously contribute to the development of two of the cancers. This elucidation enables us to reveal a significant involvement of immune traits in cancer progression, providing critical insights into how immune traits affect cancer susceptibility.

Dissecting the association between blood pressure traits, hypertension, antihypertensive medications and epilepsy: A Mendelian randomization study

BACKGROUND

Observational studies suggest that hypertension and epilepsy have a high co-occurrence, and antihypertensive medications may have impacts on the prevention and treatment of epilepsy. However, the directionality of causation between them is elusive.

METHOD

By leveraging genome-wide association studies (GWAS) summary data of each trait, we firstly performed bidirectional univariate Mendelian randomization (UVMR) to assess the strength and direction of the associations between pairs of traits, then multivariate MR (MVMR) was conducted to adjust for potential confounders in causalities. Cochran's Q statistics, leave-one-out analysis, MR-Egger regression and MR-Pleiotropy Residual Sum and Outlier methods (MR-PRESSO) were employed to evaluate the robustness of the results. Drug target MR was proceeded to assess the association between five classes of first-line antihypertensive medications and epilepsy. Specifically, single nucleotide polymorphisms (SNPs) extracted from GWAS data on systolic blood pressure (SBP)/diastolic blood pressure (DBP), along with expression quantitative trait loci (eQTL) were utilized as proxies for antihypertensive medications, respectively.

RESULTS

Forward UVMR results provided evidence that genetically predicted blood pressure traits and hypertension have causal effects on epilepsy, while reverse UVMR indicated no causal impacts of epilepsy on blood pressure traits or hypertension. The sensitivity analysis results were robust. The causalities between DBP, hypertension and epilepsy remained remarkable after adjustment by MVMR. Inverse-variance-weighted MR (IVW-MR) yielded evidence of positive association only between Beta-Blockers target genes based on DBP GWAS screening and epilepsy. Summary-data-based MR (SMR) identified a positive correlation between Beta-Blockers target gene ADRA1D and epilepsy risk.

CONCLUSIONS

Hypertension has a causal effect on epilepsy and managing DBP in patients with hypertension through Beta-Blockers may help prevent epilepsy.

Causal Association Between Heart Failure and Sepsis: Insights from Mendelian Randomization and Observational Studies

Purpose

We aimed to identify the association between heart failure (HF) with sepsis and its mortality through Mendelian randomization (MR) and observational studies.

Patients and Methods

In MR study, we utilized public summary statistics from genome-wide association studies (GWAS). We conducted univariable, multivariable and network MR analyses to investigate causal relationships between HF and sepsis, and mediating roles of cytokines and growth factors. We performed an observational analysis using the MIMIC-IV database. Propensity score matching (PSM) and logistic regression models were employed to explore causal relationships between HF and sepsis, besides short-, medium-, and long-term mortality associated with sepsis.

Results

In univariable MR analysis, there was a causal relationship between genetically predicted HF (OR = 1.15, 95% CI = 1.02-1.29, P = 0.025) and sepsis. In multivariable and network MR analyses, βNGF was independently associated with sepsis. And it mediated 17.6% (95% CI 2.45-30.72%) of HF effect on sepsis. In the real-world observational study, acute on chronic diastolic (congestive) heart failure (DCHF) (OR = 1.59, 95% CI = 1.31-1.93, P < 0.001), acute DCHF (OR = 2.52, 95% CI = 1.61-3.95, P = 0.010), and acute diastolic heart failure (DHF) (OR = 1.52, 95% CI = 1.06-2.19, P = 0.024) after PSM were associated with occurrence of sepsis. Chronic systolic (congestive) heart failure (SCHF) was associated with increased 28-day (OR = 1.75, 95% CI = 1.06-2.91, P = 0.030), 1-year (OR = 1.80, 95% CI = 1.08-3.00, P = 0.023), and 2-year (OR = 1.86, 95% CI = 1.12-3.10, P = 0.018) mortality in sepsis.

Conclusion

Observational and MR analyses showed a causal relationship between HF and sepsis. Chronic SCHF was related to increased short/long-term mortality in sepsis. Our study indicated βNGF a key factor in HF-induced sepsis.

Evidence of symptom specificity for depression in multiple sclerosis: A two sample Mendelian randomization study

BACKGROUND

Depression is common and phenotypically heterogenous in multiple sclerosis (MS). MS may increase risk of some but not all affective symptoms or certain symptoms may predispose individuals to higher MS risk.

OBJECTIVE

To assess the existence and direction of causality between distinct depressive symptoms and MS using two-sample Mendelian randomization (MR).

METHODS

Using summary data from genome-wide association studies, we selected genetic instrument variables (IV) for MS (n = 115,776) and IVs for depressive symptoms (average n = 117,713): anhedonia, altered appetite, concentration, depressed mood, fatigue, inadequacy, psychomotor changes, sleeping problems and suicidality. We performed two-sample MR in either direction using inverse-variance models. Sensitivity analyses included weighted-median and MR-Egger regression. Obesity is a known risk factor for MS and depression; we adjusted for body mass index in multivariable-MR.

RESULTS

Genetic liability to MS was associated with anhedonia (IVW estimate per 102: 0.69; 95 % CI: 0.24-1.13; p = 0.002), concentration difficulty (0.66; 0.19-1.13; p = 0.006) and psychomotor changes (0.37; 0.08-0.65; p = 0.01). Results were similar in sensitivity analyses. In the opposite direction, we found no evidence of a causal relationship for any affective symptom on MS risk.

CONCLUSIONS

Genetic susceptibility to MS was associated with anhedonia, concentration, and psychomotor-related symptoms, suggesting a specific phenotype of depression in MS.

Mediating pathways between attention deficit hyperactivity disorder and type 2 diabetes mellitus: evidence from a two-step and multivariable Mendelian randomization study

AIMS

Type 2 diabetes (T2D) is a global health burden, more prevalent among individuals with attention deficit hyperactivity disorder (ADHD) compared to the general population. To extend the knowledge base on how ADHD links to T2D, this study aimed to estimate causal effects of ADHD on T2D and to explore mediating pathways.

METHODS

We applied a two-step, two-sample Mendelian randomization (MR) design, using single nucleotide polymorphisms to genetically predict ADHD and a range of potential mediators. First, a wide range of univariable MR methods was used to investigate associations between genetically predicted ADHD and T2D, and between ADHD and the purported mediators: body mass index (BMI), childhood obesity, childhood BMI, sedentary behaviour (daily hours of TV watching), blood pressure (systolic blood pressure, diastolic blood pressure), C-reactive protein and educational attainment (EA). A mixture-of-experts method was then applied to select the MR method most likely to return a reliable estimate. We used estimates derived from multivariable MR to estimate indirect effects of ADHD on T2D through mediators.

RESULTS

Genetically predicted ADHD liability associated with 10% higher odds of T2D (OR: 1.10; 95% CI: 1.02, 1.18). From nine purported mediators studied, three showed significant individual mediation effects: EA (39.44% mediation; 95% CI: 29.00%, 49.73%), BMI (44.23% mediation; 95% CI: 34.34%, 52.03%) and TV watching (44.10% mediation; 95% CI: 30.76%, 57.80%). The combination of BMI and EA explained the largest mediating effect (53.31%, 95% CI: -1.99%, 110.38%) of the ADHD-T2D association.

CONCLUSIONS

These findings suggest a potentially causal, positive relationship between ADHD liability and T2D, with mediation through higher BMI, more TV watching and lower EA. Intervention on these factors may thus have beneficial effects on T2D risk in individuals with ADHD.

Association of gut microbiota with critical pneumonia: A two-sample Mendelian randomization study

This study investigated the causal effect of gut microbiota on critical pneumonia. Data came from a large-scale gut microbiota data set (n = 18,340) and the critical pneumonia genome-wide genotyping array (cases n = 2758 and controls n = 42,8607). Inverse variance weighting was used as the primary Mendelian randomization (MR) analysis method. Weighted median, MR-Egger, simple model, weighted model, and MR-Egger, were used to evaluate robustness. Sensitivity analysis used Cochran Q test, MR-Egger intercept test, and MR-PRESSO. For critical pneumonia, inverse variance weighting estimates suggested that Class Verrucomicrobiae (OR = 0.415; 95% CI: 0.207, 0.833; P = .013), Family Verrucomicrobiaceae (OR = 0.415; 95% CI: 0.207, 0.833; P = .013), Genus Akkermansia (OR = 0.415; 95% CI: 0.207, 0.833; P = .013), Genus LachnospiraceaeFCS020group (OR = 0.449; 95% CI: 0.230, 0.890; P = .021), Genus Parasutterella (OR = 0.466; 95% CI: 0.233, 0.929; P = .030), Genus Prevotella7 (OR = 0.645; 95% CI: 0.432, 0.960; P = .031), Order Verrucomicrobiales (OR = 0.415; 95% CI: 0.207, 0.833; P = .013), and Phylum Cyanobacteria (OR = 0.510; 95% CI: 0.272, 0.956; P = .036) had a reduced risk, while Family Enterobacteriaceae (OR = 2.746; 95% CI: 1.008, 7.474; P = .048), Genus RuminococcaceaeUCG003 (OR = 2.811; 95% CI: 1.349, 5.851; P = .006) and Order Enterobacteriales (OR = 2.746; 95% CI: 1.008, 7.474; P = .048) were associated with an increased risk. Sensitivity analyses confirmed that the aforementioned correlations were robust.

Association between coffee consumption and metabolic syndrome: A cross-sectional and Mendelian randomization study

BACKGROUND

This study investigates the associations between coffee consumption and metabolic syndrome and its components, as well as the effect of milk, sugar, and artificial sweeteners on these associations.

METHODS

A cross-sectional analysis was conducted with 351805 UK Biobank participants. Coffee consumption data were collected via food frequency questionnaires and 24-h recall. Metabolic syndrome was identified through blood biochemistry and self-reported medication use. Odds ratios were calculated using multivariable logistic regression, and results were verified with two-sample Mendelian randomization.

RESULTS

Consuming up to two cups of coffee per day was inversely associated with metabolic syndrome (1 cup/day: odds ratio [OR]: 0.88, 95% confidence interval [CI]: 0.85-0.92; 2 cups/day: OR: 0.90, 95% CI: 0.86-0.93). Higher intakes showed near-null associations. Mendelian randomization did not support a causal link between coffee intake and metabolic syndrome. Both self-reported and genetically predicted high coffee consumption (four cups per day or more) were associated with central obesity. The inverse association between coffee consumption and metabolic syndrome was more profound among drinkers of ground coffee than those of instant coffee. Results were similar when stratified by the use of milk and sugar, yet the use of artificial sweetener with coffee was positively associated with metabolic syndrome and all component conditions.

CONCLUSIONS

Coffee consumption may increase the risk of central obesity but is unlikely to impact the risk of metabolic syndrome. The potential health effects of artificial sweeteners in coffee need further investigation.

Genetic analysis from multiple cohorts implies causality between 2200 druggable genes, telomere length, and leukemia

BACKGROUND

Clinical therapeutic targets for leukemia remain to be identified and the causality between leukemia and telomere length is unclear.

METHODS

This work employed cis expression quantitative trait locus (eQTL) for 2,200 druggable genes from the eQTLGen Consortium and genome-wide association studies (GWAS) summary data for telomere length in seven blood cell types from the UK Biobank, Netherlands Cohort as exposures. GWAS data for lymphoid leukemia (LL) and myeloid leukemia (ML) from FinnGen and Lee Lab were used as outcomes for discovery and replication cohorts, respectively. Robust Mendelian randomization (MR) findings were generated from seven MR models and a series of sensitivity analyses. Summary-data-based MR (SMR) analysis and transcriptome-wide association studies (TWAS) were further implemented to verify the association between identified druggable genes and leukemia. Single-cell type expression analysis was employed to identify the specific expression of leukemia casual genes on human bone marrow and peripheral blood immune cells. Multivariable MR analysis, linkage disequilibrium score regression (LDSC), and Bayesian colocalization analysis were performed to further validate the relationship between telomere length and leukemia. Mediation analysis was used to assess the effects of identified druggable genes affecting leukemia via telomere length. Phenome-wide MR (Phe-MR) analysis for assessing the effect of leukemia causal genes and telomere length on 1,403 disease phenotypes.

RESULTS

Combining the results of the meta-analysis for MR estimates from two cohorts, SMR and TWAS analysis, we identified five LL causal genes (TYMP, DSTYK, PPIF, GDF15, FAM20A) and three ML causal genes (LY75, ADA, ABCA2) as promising drug targets for leukemia. Univariable MR analysis showed genetically predicted higher leukocyte telomere length increased the risk of LL (odds ratio [OR] = 2.33, 95 % confidence interval [95 % CI] 1.70-3.18; P = 1.33E-07), and there was no heterogeneity and horizontal pleiotropy. Evidence from the meta-analysis of two cohorts strengthened this finding (OR = 1.88, 95 % CI 1.06-3.05; P = 0.01). Multivariable MR analysis showed the causality between leukocyte telomere length and LL without interference from the other six blood cell telomere length (OR = 2.72, 95 % CI 1.88-3.93; P = 1.23E-07). Evidence from LDSC supported the positive genetic correlation between leukocyte telomere length and LL (rg = 0.309, P = 0.0001). Colocalization analysis revealed that the causality from leukocyte telomere length on LL was driven by the genetic variant rs770526 in the TERT region. The mediation analysis via two-step MR showed that the causal effect from TYMP on LL was partly mediated by leukocyte telomere length, with a mediated proportion of 12 %.

CONCLUSION

Our study identified several druggable genes associated with leukemia risk and provided new insights into the etiology and drug development of leukemia. We also found that genetically predicted higher leukocyte telomere length increased LL risk and its potential mechanism of action.

The causal association between type 2 diabetes and spinal stenosis: A Mendelian randomization analysis

Spinal stenosis is a prevalent degenerative spinal disease and one of the main causes of pain and dysfunction in older adults. Substantial evidence indicates a potentially relevant association between type 2 diabetes mellitus (T2DM) and spinal stenosis. However, the causality between these 2 disorders remains unclear. Therefore, we intended to elucidate this relationship using Mendelian Randomization (MR) analysis in this study. Based on genome-wide association study (GWAS) data on T2DM and spinal stenosis, we performed a bidirectional 2-sample MR analysis to evaluate the causality of T2DM and spinal stenosis. We assessed heterogeneity using Cochran's Q statistic and horizontal pleiotropy using the MR-Egger-intercept. "Leave-one-out" analysis was performed to determine the reliability of causal relationships. In addition, we conducted multivariate MR to clarify the direct influence of T2DM on spinal stenosis after accounting for the effect of body mass index (BMI) on spinal stenosis. Our results indicated that Individuals with T2DM had a heightened risk of spinal stenosis (odds ratio [OR]: 1.050; 95% CI: 1.004-1.098, P = .031). Moreover, no reverse causality existed between T2DM and spinal stenosis. The results of the sensitivity analysis suggest that causality is steady and robust. Multivariate MR results demonstrated that the causality of T2DM on spinal stenosis was not related to BMI (OR, 1.047; 95% CI: 1.003-1.093; P = .032). MR analyses demonstrated a possible positive causal relationship between T2DM and spinal stenosis and that this causality was unrelated to BMI.

A metabolomic profile of biological aging in 250,341 individuals from the UK Biobank

The metabolomic profile of aging is complex. Here, we analyse 325 nuclear magnetic resonance (NMR) biomarkers from 250,341 UK Biobank participants, identifying 54 representative aging-related biomarkers associated with all-cause mortality. We conduct genome-wide association studies (GWAS) for these 325 biomarkers using whole-genome sequencing (WGS) data from 95,372 individuals and perform multivariable Mendelian randomization (MVMR) analyses, discovering 439 candidate "biomarker - disease" causal pairs at the nominal significance level. We develop a metabolomic aging score that outperforms other aging metrics in predicting short-term mortality risk and exhibits strong potential for discriminating aging-accelerated populations and improving disease risk prediction. A longitudinal analysis of 13,263 individuals enables us to calculate a metabolomic aging rate which provides more refined aging assessments and to identify candidate anti-aging and pro-aging NMR biomarkers. Taken together, our study has presented a comprehensive aging-related metabolomic profile and highlighted its potential for personalized aging monitoring and early disease intervention.

Causal relationships between dyslexia and the risk of eight dementias

Observational and genetic studies have reported the relationship between dyslexia and Alzheimer's disease (AD). Until now, the causal effect of dyslexia on AD risk has remained unclear. We conducted a two-sample univariable Mendelian randomization (MR) analysis to determine the causal association between dyslexia and the risk of AD, vascular dementia (VD), Lewy body dementia (LBD), and frontotemporal dementia (FTD) and its four subtypes. First, we selected 42 dyslexia genetic variants from a large-scale genome-wide association studies (GWAS) dataset and extracted their corresponding GWAS summary statistics from AD, VD, LBD, and FTD. Second, we selected four MR methods, including inverse-variance weighted (IVW), weighted median, MR-Egger, and MR-PRESSO. Heterogeneity, horizontal pleiotropy, and leave-one-out sensitivity analysis were then used to evaluate the reliability of all causal estimates. We also conducted multivariable MR (MVMR) and mediation analysis to assess the potential mediating role of cognitive performance (CP) or educational achievement (EA) on the causal association between dyslexia and AD. Two MVMR methods, including MV IVW and MV-Egger, and two-step MR were used to perform the analysis. Using IVW, we found a significant causal association between increased dyslexia and increased risk of AD (OR = 1.15, 95% CI: 1.04-1.28, P = 0.006), but not VD, LBD, FTD, or its four subtypes. MR-PRESSO further supported the statistically significant association between dyslexia and AD (OR = 1.15, 95% CI: 1.05-1.27, P = 0.006). All sensitivity analyses confirmed the reliability of causal estimates. Using MV IVW and mediation analysis, we found no causal relationship between dyslexia and AD after adjusting for CP but not EA, CP mediated the total effect of dyslexia on AD with a proportion of 46.32%. We provide genetic evidence to support a causal effect of increased dyslexia on increased risk of AD, which was largely mediated by CP. Reading activity may be a potential intervention strategy for AD by improving cognitive function.

Causal associations between gut microbiota, circulating inflammatory proteins, and epilepsy: a multivariable Mendelian randomization study

Background

Previous studies have suggested that gut microbiota (GM) may be involved in the pathogenesis of epilepsy through the microbiota-gut-brain axis (MGBA). However, the causal relationship between GM and different epilepsy subtypes and whether circulating inflammatory proteins act as mediators to participate in epileptogenesis through the MGBA remain unclear. Therefore, it is necessary to identify specific GM associated with epilepsy and its subtypes and explore their underlying inflammatory mechanisms for risk prediction, personalized treatment, and prognostic monitoring of epilepsy.

Methods

We hypothesized the existence of a pathway GM-inflammatory proteins-epilepsy. We found genetic variants strongly associated with GM, circulating inflammatory proteins, epilepsy and its subtypes, including generalized and partial seizures, from large-scale genome-wide association studies (GWAS) summary data and used Multivariate Mendelian Randomization to explore the causal relationship between the three and whether circulating inflammatory proteins play a mediating role in the pathway from GM to epilepsy, with inverse variance weighted (IVW) method as the primary statistical method, supplemented by four methods: MR-Egger, weighted median estimator (WME), Weighted mode and Simple mode.

Results

16 positive and three negative causal associations were found between the genetic liability of GM and epilepsy and its subtypes. There were nine positive and nine negative causal associations between inflammatory proteins and epilepsy and its subtypes. Furthermore, we found that C-X-C motif chemokine 11 (CXCL11) levels mediated the causal association between Genus Family XIII AD3011 group and epilepsy.

Conclusion

Our study highlights the possible causal role of specific GM and specific inflammatory proteins in the development of epilepsy and suggests that circulating inflammatory proteins may mediate epileptogenesis through the MGBA.

Smoking and alcohol by HPV status in head and neck cancer: a Mendelian randomization study

HPV-positive and HPV-negative head and neck squamous cell carcinoma (HNSCC) are recognized as distinct entities. There remains uncertainty surrounding the causal effects of smoking and alcohol on the development of these two cancer types. Here we perform multivariable Mendelian randomization (MR) to evaluate the causal effects of smoking and alcohol on the risk of HPV-positive and HPV-negative HNSCC in 3431 cases and 3469 controls. Lifetime smoking exposure, as measured by the Comprehensive Smoking Index (CSI), is associated with increased risk of both HPV-negative HNSCC (OR = 3.03, 95%CI:1.75-5.24, P = 7.00E-05) and HPV-positive HNSCC (OR = 2.73, 95%CI:1.39-5.36, P = 0.003). Drinks Per Week is also linked with increased risk of both HPV-negative HNSCC (OR = 7.72, 95%CI:3.63-16.4, P = 1.00E-07) and HPV-positive HNSCC (OR = 2.66, 95%CI:1.06-6.68, P = 0.038). Smoking and alcohol independently increase the risk of both HPV-positive and HPV-negative HNSCC. These findings have important implications for understanding the modifying risk factors between HNSCC subtypes.

Can Omega-3 prevent the accidence of stroke: a mendelian randomization study

BACKGROUND

The lipid-lowering effects of Omega-3 fatty acids have been widely reported, yet their impact on ischemic stroke remains controversial. Reports on the protective effects of unsaturated fatty acids, such as Omega-6 and Omega-7, as well as saturated fatty acids in cardiovascular diseases, including hypertension and ischemic stroke, are less frequent.

OBJECTIVES

This study aims to identify fatty acids associated with blood pressure and ischemic stroke through Mendelian randomization. Besides, it seeks to determine whether specific fatty acids can prevent ischemic stroke by managing blood pressure and revealing the specific mechanisms of this action.

METHODS

This research involved downloading relevant data from websites and extracting SNPs that met the standard criteria as instrumental variables. Simultaneously, the 'MR-PRESSO' package and 'Mendelian Randomization' package were used to eliminate confounding SNPs that could bias the study results. Then, inverse variance weighting and the weighted median were employed as primary analysis methods, accompanied by sensitivity analysis to assess the validity of the causal relationships. Initially, multivariable Mendelian randomization was used to identify fatty acids linked to blood pressure and the incidence of ischemic stroke. The causal link between certain fatty acids and the initiation of ischemic stroke was then investigated using bidirectional and mediator Mendelian randomization techniques. Stepwise Regression and the Product of Coefficients Method in mediator Mendelian randomization were utilized to ascertain whether specific fatty acids reduce ischemic stroke risk by lowering blood pressure.

RESULTS

Multivariable Mendelian randomization analysis indicated a potential inverse correlation between Omega-3 intake and both blood pressure and ischemic stroke. Consequently, Omega-3 was selected as the exposure, with blood pressure and ischemic stroke-related data as outcomes, for further bidirectional and mediation Mendelian Randomization analyses. Bidirectional Mendelian Randomization revealed that Omega-3 significantly influences DBP (P = 1.01e-04) and IS (P = 0.016). It also showed that DBP and SBP significantly affect LAS, SVS, CES, IS, and LS. Mediator Mendelian Randomization identified five established mediating pathways: Omega-3-Diastolic blood pressure-Small vessel stroke, Omega-3-Diastolic blood pressure-Cardioembolic stroke, Omega-3-Diastolic blood pressure-Lacunar stroke, Omega-3-Diastolic blood pressure-Large artery atherosclerosis stroke, and Omega-3-Diastolic blood pressure-Ischemic stroke. Of these, four pathways are complete mediation, and one pathway is partial mediation.

CONCLUSIONS

The findings suggest that Omega-3 may indirectly reduce the incidence of ischemic stroke by lowering blood pressure. Thus, blood pressure modulation might be one of the mechanisms through which Omega-3 prevents ischemic stroke. In summary, incorporating an increased intake of Omega-3 in the diet can serve as one of the dietary intervention strategies for patients with hypertension. Additionally, it can act as an adjunctive therapy for the prevention of ischemic strokes and their complications.

The role of the gluteofemoral adipose tissue in cerebrovascular disease risk: evidence from a mendelian randomization and mediation analysis

Objective

To explore causal associations between BMI-independent body fat distribution profiles and cerebrovascular disease risk, and to investigate potential mediators underlying these associations.

Methods

Leveraging data from genome wide association studies of BMI-independent gluteofemoral (GFAT), abdominal subcutaneous (ASAT), and visceral (VAT) adipose tissue volumes in UK Biobank, we selected variants associated with each trait, and performed univariable and multivariable mendelian randomization (MR) analyses on ischemic stroke and subtypes (large artery (LAS), cardioembolic (CES), small vessel (SVS)). We used coronary artery disease (CAD), carotid intima media thickness (cIMT), and an MRI-confirmed lacunar stroke as positive controls. For significant associations, we explored the mediatory role of four possible mediator categories in mediation MR analyses.

Results

Higher genetically proxied, BMI-independent GFAT volume was associated with decreased risk of ischemic stroke (FDR-p=0.0084), LAS (FDR-p=0.019), SVS (FDR-p<0.001), CAD (FDR-p<0.001), MRI-confirmed lacunar stroke (FDR-p=0.0053), and lower mean cIMT (FDR-p=0.0023), but not CES (FDR-p=0.749). Associations were largely consistent in pleiotropy- and sample structure-robust analyses. No association was observed between genetically proxied ASAT or VAT volumes and ischemic stroke/subtypes risk. In multivariable MR analyses, GFAT showed the most consistent independent association with ischemic stroke, LAS, and SVS. Common vascular risk factors were the predominant mediators in the GFAT-cerebrovascular disease axis, while adipose-tissue-specific adiponectin and leptin mediated a proportion of ischemic stroke and CAD risk.

Interpretation

Genetically proxied, BMI-independent higher GFAT volume is associated with reduced cerebrovascular disease risk. Although this is largely mediated by common vascular risk factor modification, targeting adipose-tissue specific pathways may provide additional cardiovascular benefit.

An integrative multi-context Mendelian randomization method for identifying risk genes across human tissues

Mendelian randomization (MR) provides valuable assessments of the causal effect of exposure on outcome, yet the application of conventional MR methods for mapping risk genes encounters new challenges. One of the issues is the limited availability of expression quantitative trait loci (eQTLs) as instrumental variables (IVs), hampering the estimation of sparse causal effects. Additionally, the often context- or tissue-specific eQTL effects challenge the MR assumption of consistent IV effects across eQTL and GWAS data. To address these challenges, we propose a multi-context multivariable integrative MR framework, mintMR, for mapping expression and molecular traits as joint exposures. It models the effects of molecular exposures across multiple tissues in each gene region, while simultaneously estimating across multiple gene regions. It uses eQTLs with consistent effects across more than one tissue type as IVs, improving IV consistency. A major innovation of mintMR involves employing multi-view learning methods to collectively model latent indicators of disease relevance across multiple tissues, molecular traits, and gene regions. The multi-view learning captures the major patterns of disease relevance and uses these patterns to update the estimated tissue relevance probabilities. The proposed mintMR iterates between performing a multi-tissue MR for each gene region and joint learning the disease-relevant tissue probabilities across gene regions, improving the estimation of sparse effects across genes. We apply mintMR to evaluate the causal effects of gene expression and DNA methylation for 35 complex traits using multi-tissue QTLs as IVs. The proposed mintMR controls genome-wide inflation and offers insights into disease mechanisms.

Mendelian randomization supports causal effects of inflammatory biomarkers on myopic refractive errors

AIMS

To determine whether inflammatory biomarkers are causal risk factors for more myopic refractive errors.

METHODS

Northern Sweden Population Health Study (NSPHS), providing inflammatory biomarkers data; UK Biobank, providing refractive errors data. 95,619 European men and women aged 40 to 69 years with available information of refractive errors and inflammatory biomakers. Inflammatory biomarkers including ADA, CCL23, CCL25, CD6, CD40, CDCP-1, CST5, CXCL-5, CXCL-6, CXCL-10, IL-10RB, IL-12B, IL-15RA, IL-18R1, MCP-2, MMP-1, TGF-β1, TNF-β, TWEAK and VEGF-A were exposures, and spherical equivalent (SE) using the formula SE = sphere + (cylinder/2) was outcome.

RESULTS

Mendelian randomization analyses showed that each unit increase in VEGF-A, CD6, MCP-2 were causally related to a more myopic refractive errors of 0.040 D/pg.mL-1 (95% confidence interval 0.019 to 0.062; P = 2.031 × 10-4), 0.042 D/pg.mL-1 (0.027 to 0.057; P = 7.361 × 10-8) and 0.016 D/pg.mL-1 (0.004 to 0.028; P = 0.009), and each unit increase in TWEAK was causally related to a less myopic refractive errors of 0.104 D/pg.mL-1 (-0.152 to -0.055; P = 2.878 × 10-5). Tested by the MR-Egger, weighted median, MR-PRESSO, Leave-one-out methods, our results were robust to horizontal pleiotropy and heterogeneity in VEGF-A, MCP-2, CD6, but not in TWEAK.

CONCLUSIONS

Our Mendelian Randomization analysis supported the causal effects of VEGF-A, MCP-2, CD6 and TWEAK on myopic refractive errors. These findings are important for providing new indicators for early intervention of myopia to make myopic eyesight threatening consequences less inevitable.

Causal associations of central and peripheral risk factors with knee osteoarthritis: a longitudinal and Mendelian Randomisation study using UK Biobank data

ABSTRACT

Our aim was to investigate relative contributions of central and peripheral mechanisms to knee osteoarthritis (OA) diagnosis and their independent causal association with knee OA. We performed longitudinal analysis using data from UK-Biobank participants. Knee OA was defined using International Classification of Diseases manual 10 codes from participants' hospital records. Central mechanisms were proxied using multisite chronic pain (MCP) and peripheral mechanisms using body mass index (BMI). Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated, and proportional risk contribution (PRC) was estimated from receiver-operator-characteristic (ROC) analysis. To estimate the causal effects, we performed 2-sample multivariable Mendelian Randomisation (MR) analysis. We selected genetic instruments from the largest Genome Wide Association Study of BMI (N = 806,834) and MCP (N = 387,649) and estimated the instruments genetic associations with knee OA in the largest available dataset (62,497 cases and 333,557 control subjects). The multivariable MR was performed using modified inverse-variance weighting methods. Of the 203,410 participants, 6% developed knee OA. Both MCP (OR 1.23, 95% CI; 1.21-1.24) and BMI (1.10, 95% CI; 1.10-1.11) were associated with knee OA diagnosis. The PRC was 6.9% (95% CI; 6.7%-7.1%) for MCP and 21.9% (95% CI; 21.4%-22.5%) for BMI; the combined PRC was 38.8% (95% CI; 37.9%-39.8%). Body mass index and MCP had independent causal effects on knee OA (OR 1.76 [95% CI, 1.64-1.88] and 1.83 [95% CI, 1.54-2.16] per unit change, respectively). In conclusion, peripheral risk factors (eg, BMI) contribute more to the development of knee OA than central risk factors (eg, MCP). Peripheral and central factors are independently causal on knee OA.

The plasma lipids with different fatty acid chains are associated with the risk of hemorrhagic stroke: a Mendelian randomization study

Background and objective

Hemorrhagic stroke, characterized by acute bleeding due to cerebrovascular lesions, is associated with plasma lipids and endothelial damage. The causal relationship between genetic plasma lipid levels and hemorrhagic stroke remains unclear. This study employs a two-sample Mendelian randomization (MR) analysis to explore the causal relationship between plasma lipid profiles with different fatty acid chains and the risk of intracerebral and subarachnoid hemorrhage, the two main subtypes of hemorrhagic stroke.

Methods

The datasets for exposure and outcome summary statistics were obtained from publicly available sources such as the GWAS Catalog, IEU OpenGWAS project, and FinnGen. The two-sample MR analysis was employed to initially assess the causal relationship between 179 plasma lipid species and the risk of intracerebral and subarachnoid hemorrhage in the Finnish population, leading to the identification of candidate lipids. The same methods were applied to reanalyze data from European populations and conduct a meta-analysis of the candidate lipids. The Inverse Variance Weighting (IVW) method served as the primary analysis for causal inference, with additional methods used for complementary analyses. Sensitivity analysis was conducted to clarify causal relationships and reduce biases.

Results

Two analyses using Mendelian randomization were performed, followed by meta-analyses of the results. A causal relationship was established between 11 specific lipid species and the occurrence of intracerebral hemorrhage within the European population. Additionally, 5 distinct lipid species were associated with subarachnoid hemorrhage. Predominantly, lipids with linoleic acid and arachidonic acid side chains were identified. Notably, lipids containing arachidonic acid chains (C20:4) such as PC 18:1;0_20:4;0 consistently showed a decreased risk of both intracerebral hemorrhage [p < 0.001; OR(95% CI) = 0.892(0.835-0.954)] and subarachnoid hemorrhage [p = 0.002; OR(95% CI) = 0.794(0.689-0.916)]. Conversely, lipids with linoleic acid chains (C18:2) were associated with an increased risk of intracerebral hemorrhage.

Conclusion

This study identifies a potential causal relationship between lipids with different fatty acid side chains and the risk of intracerebral and subarachnoid hemorrhagic stroke, improving the understanding of the mechanisms behind the onset and progression of hemorrhagic stroke.

Genetic predisposition to type 2 diabetes mellitus and aortic dissection: a Mendelian randomisation study

Background

This Mendelian randomization (MR) study aimed to explore the causal relationship between the genetic predisposition to type 2 diabetes mellitus (T2DM) and aortic dissection (AD), and to assess associations with genetically predicted glycemic traits. The study sought to verify the inverse relationship between T2DM and AD using a more robust and unbiased method, building on the observational studies previously established.

Materials and methods

The study employed a two-sample and multivariable MR approach to analyze genetic data from the DIAbetes Meta-ANalysis of Trans-Ethnic association studies (DIAMANTE) with 74,124 cases and 824,006 controls, and the Meta-Analyses of Glucose and Insulin-Related Traits Consortium (MAGIC) involving up to 196,991 individuals. For AD data, FinnGen Release 10 was used, including 967 cases and 381,977 controls. The research focused on three foundational MR assumptions and controlled for confounders like hypertension. Genetic instruments were selected for their genome-wide significance, and multiple MR methods and sensitivity analyses were conducted.

Results

The study revealed no significant effect of genetic predisposition to T2DM on the risk of AD. Even after adjusting for potential confounders, the results were consistent, indicating no causal relationship. Additionally, glycemic traits such as fasting glucose, fasting insulin, and HbA1c levels did not show a significant impact on AD susceptibility. The findings remained stable across various MR models and sensitivity analyses. In contrast, genetic liability to T2DM and glycemic traits showed a significant association with coronary artery disease (CAD), aligning with the established understanding.

Conclusion

Contrary to previous observational studies, this study concludes that genetic predisposition to T2DM does not confer protection against AD. These findings underscore the imperative for further research, particularly in exploring the preventative potential of T2DM treatments against AD and to facilitate the development of novel therapeutic interventions.

MRBEE: A bias-corrected multivariable Mendelian randomization method

Mendelian randomization (MR) is an instrumental variable approach used to infer causal relationships between exposures and outcomes, which is becoming increasingly popular because of its ability to handle summary statistics from genome-wide association studies. However, existing MR approaches often suffer the bias from weak instrumental variables, horizontal pleiotropy and sample overlap. We introduce MRBEE (MR using bias-corrected estimating equation), a multivariable MR method capable of simultaneously removing weak instrument and sample overlap bias and identifying horizontal pleiotropy. Our extensive simulations and real data analyses reveal that MRBEE provides nearly unbiased estimates of causal effects, well-controlled type I error rates and higher power than comparably robust methods and is computationally efficient. Our real data analyses result in consistent causal effect estimates and offer valuable guidance for conducting multivariable MR studies, elucidating the roles of pleiotropy, and identifying total 42 horizontal pleiotropic loci missed previously that are associated with myopia, schizophrenia, and coronary artery disease.

Association between obstructive sleep apnea and risk of lung cancer: findings from a collection of cohort studies and Mendelian randomization analysis

Background

Previous cohort studies conducted on large populations have suggested a potential association between obstructive sleep apnea (OSA) and an elevated risk of developing lung cancer. However, limited research has comprehensively investigated the correlation between the two conditions, and the causal effect remains unknown.

Methods

A comprehensive and systematic search was conducted across various databases, including PubMed, Web of Science, Cochrane Library, and Embase, from their inception dates to November 1, 2023. To assess the relationship between OSA and lung cancer, a meta-analysis was performed. Additionally, a two-sample Mendelian randomization (MR) study was conducted using summary data. The datasets included 336,659 individuals from the FinnGen study for OSA and 27,209 individuals from the International Lung Cancer Consortium study, as well as 420,473 individuals from the UK Biobank study for lung cancer. The estimates from each study were aggregated using the inverse variance-weighted method.

Results

Data from six population-based cohort studies, encompassing 6,589,725 individuals, indicated a significant increase in the risk of developing lung cancer among patients with OSA (HR 1.28, 95% CI 1.07-1.54). However, the MR analysis did not support a causal relationship between OSA and lung cancer (OR 1.001, 95% CI 0.929-1.100). This lack of association was consistent across specific subtypes of lung cancer, including non-small-cell lung cancer (OR 1.000, 95% CI 0.999-1.000, p = 0.974), lung adenocarcinoma (OR 0.996, 95% CI 0.906-1.094, p = 0.927), and squamous cell lung carcinoma (OR 1.034, 95% CI 0.937-1.140, p = 0.507).

Conclusions

Our meta-analysis findings suggest an elevated risk of lung cancer among individuals with OSA. However, the MR analysis did not provide evidence supporting a causal relationship between OSA and lung cancer. Further investigation is required to uncover the underlying factors contributing to the observed association between OSA and lung cancer risk.

Dried fruit intake and lower risk of type 2 diabetes: a two-sample mendelian randomization study

BACKGROUND

Previous studies have shown controversy about whether dried fruit intake is associated with type 2 diabetes. This study aimed to examine the potential causal effect of dried fruit intake on type 2 diabetes by conducting a two-sample Mendelian randomization study.

METHODS

We used genome-wide association study (GWAS) summary statistics for MR analysis to explore the causal association of dried fruit intake with T2D. The inverse-variance weighted (IVW) method was used as the main analytical method for MR analysis. In addition, the MR-Egger method and the weighted median method were applied to supplement the IVW method. Furthermore, Cochrane's Q test, MR-Egger intercept test, and leave-one-out analysis were used to perform sensitivity analysis. The funnel plot was used to assess publication bias.

RESULTS

The results from the IVW analysis indicated that dried fruit intake could reduce the risk of T2D [odds ratio (OR) = 0.392, 95% confidence interval (CI): 0.241-0.636, p-value = 0.0001]. In addition, the result of additional method Weighted median is parallel to the effects estimated by IVW. Furthermore, the sensitivity analysis illustrates that our MR analysis was unaffected by heterogeneity and horizontal pleiotropy. Finally, the results of the leave-one-out method showed the robustness of our MR results. And the funnel plot shows a symmetrical distribution.

CONCLUSION

Our study provides evidence for the benefits of dried fruit intake on T2D. Therefore, a reasonable consumption of dried fruit may provide primary prevention.

Genetic correlation and causal relationship between sleep and myopia: a mendelian randomization study

Purpose

To investigate the genetic correlation and causal links between sleep traits (including sleep duration, chronotype, and insomnia) and myopia.

Methods

Summary data on three sleep traits (sleep duration, chronotype and insomnia) and myopia from FinnGen (n = 214,211) and UK Biobank (n = 460,536) were analyzed using linkage disequilibrium score regression (LD Score), univariable and multivariable mendelian randomization (MR) experiments and Causal Analysis Using Summary Effect (CAUSE) estimation.

Results

LD Score regression detected candidate genetic correlation between sleep traits and myopia, such as sleep duration, chronotype (Genetic Correlation Z-score >10.00, h2_observed_p < 0.005, Lambda GC > 1.05, p > 0.05). Univariable MR analyses indicated that increased sleep duration has a promotional effect on the occurrence of myopia (p = 0.046 < 0.05, P_FDR = 0.138 < 0.2, OR = 2.872, 95% CI: 1.018-8.101). However, after accounting for potential confounding factors, multivariable MR and CAUSE analysis did not provide evidence for a causal effect of the three sleep traits on myopia.

Conclusion

There may be a potential genetic correlation between sleep duration, chronotype and myopia. However, neither of sleep duration, chronotype or insomnia had causal effect on myopia.

Mendelian randomization analysis reveals higher whole body water mass may increase risk of bacterial infections

BACKGROUND AND PURPOSE

The association of water loading with several infections remains unclear. Observational studies are hard to investigate definitively due to potential confounders. In this study, we employed Mendelian randomization (MR) analysis to assess the association between genetically predicted whole body water mass (BWM) and several infections.

METHODS

BWM levels were predicted among 331,315 Europeans in UK Biobank using 418 SNPs associated with BWM. For outcomes, we used genome-wide association data from the UK Biobank and FinnGen consortium, including sepsis, pneumonia, intestinal infections, urinary tract infections (UTIs) and skin and soft tissue infections (SSTIs). Inverse-variance weighted MR analyses as well as a series of sensitivity analyses were conducted.

RESULTS

Genetic prediction of BWM is associated with an increased risk of sepsis (OR 1.34; 95% CI 1.19 to 1.51; P = 1.57 × 10- 6), pneumonia (OR: 1.17; 95% CI 1.08 to 1.29; P = 3.53 × 10- 4), UTIs (OR: 1.26; 95% CI 1.16 to 1.37; P = 6.29 × 10- 8), and SSTIs (OR: 1.57; 95% CI 1.25 to 1.96; P = 7.35 × 10- 5). In the sepsis and pneumonia subgroup analyses, the relationship between BWM and infection was observed in bacterial but not in viral infections. Suggestive evidence suggests that BWM has an effect on viral intestinal infections (OR: 0.86; 95% CI 0.75 to 0.99; P = 0.03). There is limited evidence of an association between BWM levels and bacteria intestinal infections, and genitourinary tract infection (GUI) in pregnancy. In addition, MR analyses supported the risk of BWM for several edematous diseases. However, multivariable MR analysis shows that the associations of BWM with sepsis, pneumonia, UTIs and SSTIs remains unaffected when accounting for these traits.

CONCLUSIONS

In this study, the causal relationship between BWM and infectious diseases was systematically investigated. Further prospective studies are necessary to validate these findings.

Gastroesophageal Reflux and Chronic Rhinosinusitis: A Mendelian Randomization Study

OBJECTIVE

Chronic rhinosinusitis (CRS) is associated with gastroesophageal reflux (GERD). However, the causal relationship is controversial. We conducted a two-sample Mendelian Randomization (MR) analysis to explore this potential association.

METHODS

Based on genome-wide association studies (GWAS), a univariable MR was performed to explore the causal relationship of GERD with CRS. Instrumental variables (IVs) pertinent to anti-GERD treatment were employed as a means of validation. The primary MR outcome was established using an inverse variance weighted (IVW) method, supplemented by multiple sensitivity analyses. Subsequently, a multivariable MR was conducted to account for potential confounding variables, thereby ascertaining a direct effect of GERD on CRS. Finally, a network MR analysis was carried out to elucidate the mediating role of asthma in the relationship between GERD and CRS.

RESULTS

The univariable MR demonstrated an association between GERD and an elevated risk of CRS (IVW OR = 1.30, 95% CI = 1.18-1.45, p = 4.19 × 10-7). Omeprazole usage was associated with a reduction in CRS risk (IVW OR = 0.64, 95% CI = 0.42-0.98, p = 0.039). The causal relationship between GERD and CRS remained after adjusting for potential confounders, such as smoking characteristics, body mass index, asthma, allergic rhinitis, in the multivariable MR analysis. Besides, the proportion of the causal effect of GERD on CRS mediated by asthma was 19.65% (95% CI = 2.69%-36.62%).

CONCLUSION

GERD was independently associated with an increased risk of CRS. The mediating role of asthma between GERD and CRS also reveals that GERD is one of the mechanisms underlying unified airway disease.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:3086-3092, 2024.

Association of ankylosing spondylitis with cardiovascular disease: a bidirectional two-sample mendelian randomization study

Backgrounds

Current observational investigations hint at a potential linkage between ankylosing spondylitis and cardiovascular wellness. However, the nature of this causality remains to be elucidated. Consequently, this study is designed to evaluate the causal interconnection between ankylosing spondylitis and cardiovascular-related conditions utilizing a bidirectional two-sample Mendelian Randomization (MR) methodology.

Methods

In this study, we conducted Mendelian randomization (MR) analyses using genome-wide association study (GWAS) data. The fixed-effects inverse variance weighted (IVW) model was used as the primary analysis method, and MR-Egger regression and the weighted median method were employed as supplementary approaches. Horizontal pleiotropy and heterogeneity were evaluated using various statistical tests, including MR-PRESSO global test, MR-Egger intercept, and Cochran's Q test.

Results

The MR result demonstrated an increased risk of heart failure in individuals with ankylosing spondylitis (OR: 1.0132, 95% CI = 1.0043-1.0221, p = 0.003). The MR analysis results did not demonstrate a causal relationship between ankylosing spondylitis and other cardiovascular diseases, such as atrial fibrillation, coronary artery disease, ischemic stroke, myocardial infarction, and valvular heart disease (all p > 0.05). No evidence of reverse causality was found between ankylosing spondylitis and mentioned cardiovascular diseases in reverse MR analyses. Sensitivity analysis verified the reliability of the results.

Conclusion

Our MR study indicates a relationship between ankylosing spondylitis and an increased risk of heart failure. Further research is needed to confirm these findings and elucidate the underlying mechanisms involved.

The causal relationship between blood cell indices and 28-day mortality in sepsis: a retrospective study and bidirectional Mendelian randomization analysis

BACKGROUND

Despite emerging evidence linking blood cell indices (BCIs) to sepsis mortality, the inconsistency of observational studies obscures the clarity of these associations. This study aims to clarify the causal influence of BCIs on 28-day mortality rates in sepsis patients.

METHODS

Utilizing univariable and multivariable Mendelian randomization (MR) analyses, we examined the impact of BCIs on sepsis mortality by analyzing data from extensive genome-wide association studies. The inverse-variance weighted (IVW) method was our primary analytic tool, complemented by several robustness checks to mitigate pleiotropy, including weighted median, mode-based estimates, MR-Egger regression, and MR-PRESSO. Subsequently, we conducted a retrospective study to further explore the correlation between platelet indices and 28-day mortality of sepsis using real-world data.

RESULTS

Our findings highlight a significant causal relationship between platelet distribution width (PDW) and 28-day mortality in sepsis, with the univariable Mendelian randomization approach yielding an odds ratio of 1.12 (95% CI, 1.06-1.26; P < 0.05). Multivariable analysis further substantiated PDW's robust association with mortality risk (OR 1.23; 95% CI, 1.03-1.48; P < 0.05). Conversely, our analysis did not uncover significant correlations between the genetic predispositions to other BCIs-including red blood cell count, erythrocyte distribution width, platelet count, mean platelet volume, white blood cell count, neutrophil count, neutrophil percentage, lymphocyte count, and lymphocyte percentage-and 28-day mortality in sepsis. Additionally, an inverse MR analysis did not establish a causal impact of 28-day mortality in sepsis on PDW (OR 1.00; 95% CI, 1.00-1.07; P = 0.29). Moreover, a similar result was observed in the retrospective study.

CONCLUSIONS

The study underscores the independent causal role of PDW in predicting 28-day mortality in sepsis, suggesting its potential utility in early patient assessment, risk stratification, and tailoring of therapeutic interventions.

Genetic analyses of the bidirectional associations between common mental disorders and asthma

Objective

Although extensive research has explored the link between mental disorders and asthma, the characteristics and patterns of this association are still unclear. Our study aims to examine the genetic causal links between common mental disorders (specifically, anxiety and depression) and asthma.

Methods

We conducted genetic analyses including linkage disequilibrium score regression (LDSC) and bidirectional two-sample Mendelian randomization (MR) analyses, and utilized summary statistics from recent large-scale Genome-Wide Association Studies (GWASs) in European populations, covering sensation of anxiety or depression, anxiety sensation, depression sensation, anxiety disorders, major depression disorder (MDD), and asthma.

Results

LDSC revealed significant genetic correlations among sensation of anxiety or depression, MDD and asthma (P < 0.017), highlighting potential genetic correlation between anxiety disorders and asthma (P < 0.05 yet > 0.017). In bidirectional two-sample MR, inverse-variance weighted (IVW) analyses suggested that genetic liability to asthma was significantly associated with an increased risk of sensation of anxiety or depression (OR = 4.760, 95%CI: 1.645-13.777), and MDD (OR = 1.658, 95%CI: 1.477-1.860). Conversely, IVW analyses indicated that genetic liability to anxiety disorders was not associated with an increased risk of asthma (P > 0.01), nor was genetic liability to asthma associated with an increased risk of anxiety disorders (P > 0.01). Furthermore, no significant genetic causal relationships were observed for other studied traits. Multivariate MR, after adjusting for body mass index and alcohol consumption, further corroborated the independent causal effect of genetic predisposition to MDD on the risk of asthma (OR = 1.460, 95% CI: 1.285-1.660).

Conclusion

Our study establishes MDD as a predisposing factor for asthma. Meanwhile, anxiety disorders are not causal risk factors for asthma, nor is the reverse true. It is recommended to closely monitor asthma symptoms in patients with MDD.

Assessing the causal relationship of birth weight and childhood obesity on osteoarthritis: a Mendelian randomization study

Obesity is associated with osteoarthritis (OA), but few studies have used fetal origin to explore the association. Our study aims to disentangle the causality between birth weight, childhood obesity, and adult OA using Mendelian randomization (MR). We identified single nucleotide polymorphisms (SNPs) related to birth weight (n = 298,142) and childhood obesity (n = 24,160) from two genome-wide association studies contributed by the Early Growth Genetics Consortium. Summary statistics of OA and its phenotypes (knee, hip, spine, hand, thumb, and finger OA) from the Genetics of Osteoarthritis Consortium (n = 826,690) were used to estimate the effects of SNPs on OA. Multivariable MR (MVMR) was conducted to investigate the independent effects of exposures. It turned out that genetically predicted standard deviation increase in birth weight was not associated with OA. In contrast, there was a marginally positive effect of childhood obesity on total [odds ratio (OR) = 1.07, 95% confidence interval (CI) = 1.00, 1.15 using IVW], knee (OR = 1.13, 95% CI = 1.05, 1.22 using weighted median), hip (OR = 1.13, 95% CI = 1.04, 1.24 using IVW), and spine OA (OR = 1.12, 95% CI = 1.03, 1.22 using IVW), but not hand, thumb, or finger OA. MVMR indicated a potential adulthood body mass index-dependent causal pathway between childhood obesity and OA. In conclusion, no association of birth weight with OA was suggested. Childhood obesity, however, showed a causality with OA in weight-bearing joints, which seems to be a general association of obesity with OA.