Causal effect of serum 25-hydroxyvitamin D levels on low back pain: A two-sample mendelian randomization study

Chronic Low Back Pain Causal Risk Factors Identified by Mendelian Randomization: a Cross-Sectional Cohort Analysis

Background Context

There are a number of risk factors- from biological, psychological, and social domains- for non-specific chronic low back pain (cLBP). Many cLBP treatments target risk factors on the assumption that the targeted factor is not just associated with cLBP but is also a cause (i.e, a causal risk factor). In most cases this is a strong assumption, primarily due to the possibility of confounding variables. False assumptions about the causal relationships between risk factors and cLBP likely contribute to the generally marginal results from cLBP treatments.

Purpose

The objectives of this study were to a) using rigorous confounding control compare associations between modifiable causal risk factors identified by Mendelian randomization (MR) studies with associations in a cLBP population and b) estimate the association of these risk factors with cLBP outcomes.

Study Design/Setting

Cross sectional analysis of a longitudinal, online, observational study.

Patient Sample

1,376 participants in BACKHOME, a longitudinal observational e-Cohort of U.S. adults with cLBP that is part of the NIH Back Pain Consortium (BACPAC) Research Program.

Outcome Measures

Pain, Enjoyment of Life, and General Activity (PEG) Scale.

Methods

Five risk factors were selected based on evidence from MR randomization studies: sleep disturbance, depression, BMI, alcohol use, and smoking status. Confounders were identified using the ESC-DAG approach, a rigorous method for building directed acyclic graphs based on causal criteria. Strong evidence for confounding was found for age, female sex, education, relationship status, financial strain, anxiety, fear avoidance and catastrophizing. These variables were used to determine the adjustment sets for the primary analysis. Potential confounders with weaker evidence were used for a sensitivity analysis.

Results

Participants had the following characteristics: age 54.9 ± 14.4 years, 67.4% female, 60% never smokers, 29.9% overweight, 39.5% obese, PROMIS sleep disturbance T-score 54.8 ± 8.0, PROMIS depression T-score 52.6 ± 10.1, Fear-avoidance Beliefs Questionnaire 11.6 ± 5.9, Patient Catastrophizing Scale 4.5 ± 2.6, PEG 4.4 ± 2.2. In the adjusted models alcohol use, sleep disturbance, depression, and obesity were associated with PEG, after adjusting for confounding variables identified via a DAG constructed using a rigorous protocol. The adjusted effect estimates- the expected change in the PEG outcome for every standard deviation increase or decrease in the exposure (or category shift for categorical exposures) were the largest for sleep disturbance and obesity. Each SD increase in the PROMIS sleep disturbance T-score resulted in a mean 0.77 (95% CI: 0.66, 0.88) point increase in baseline PEG score. Compared to participants with normal BMI, adjusted mean PEG score was slightly higher by 0.37 points (95% CI: 0.09, 0.65) for overweight participants, about 0.8 to 0.9 points higher for those in obesity classes I and II, and 1.39 (95% CI: 0.98, 1.80) points higher for the most obese participants. Each SD increase in the PROMIS depression T-score was associated with a mean 0.28 (95% CI: 0.17, 0.40) point increase in baseline PEG score, while each SD decrease in number of alcoholic drinks per week resulted in a mean 0.12 (95%CI: 0.01, 0.23) increase in baseline PEG score in the adjusted model.

Conclusions

Several modifiable causal risk factors for cLBP - alcohol use, sleep disturbance, depression, and obesity- are associated with PEG, after adjusting for confounding variables identified via a DAG constructed using a rigorous protocol. Convergence of our findings for sleep disturbance, depression, and obesity with the results from MR studies, which have different designs and biases, strengthens the evidence for causal relationships between these risk factors and cLBP (1). The estimated effect of change in a risk factors on change in PEG were the largest for sleep disturbance and obesity. Future analyses will evaluate these relationships with longitudinal data.

Causality between herpes virus infections and allograft dysfunction after tissue and organ transplantation: a two-sample bidirectional Mendelian randomization study

Background

Observational studies have suggested that herpes virus infections increase the risk of allograft dysfunction after tissue and organ transplantation, but it is still unclear whether this association is causal. The aim of this study was to assess the causal relationship between four herpes virus infections and allograft dysfunction.

Methods

We used two-sample bidirectional Mendelian randomization (MR) to investigate the causality between four herpes virus infections - cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus (HSV) and varicella zoster virus (VZV) - and allograft dysfunction after tissue and organ transplantation. Based on summary data extracted from genome-wide association studies (GWAS), we chose eligible single nucleotide polymorphisms (SNPs) as instrumental variables. The Inverse variance weighted (IVW) method was used as the main analysis method, supplemented by Weighted median and MR-Egger analyses. The MR-PRESSO test, MR-Egger intercept test, heterogeneity test, leave-one-out analysis and funnel plot were used to analyze the sensitivity of MR results.

Results

We found EBV early antigen-D (EA-D) antibody levels and shingles were the only two variables associated with an increased risk of allograft dysfunction. No evidence of allograft dysfunction increasing the risk of the four herpes virus infections was observed. Sensitivity analyses confirmed the robustness of our results.

Conclusions

Our results suggest that EBV and VZV are involved in graft rejection or dysfunction. However, the relationship between CMV and HSV infections and allograft dysfunction remains unclear and requires further clarification.

Associations between lifestyle-related risk factors and back pain: a systematic review and meta-analysis of Mendelian randomization studies

BACKGROUND

Mendelian randomization (MR) studies have an advantage over conventional observational studies when studying the causal effect of lifestyle-related risk factors on back pain. However, given the heterogeneous design of existing MR studies on back pain, the reported causal estimates of these effects remain equivocal, thus obscuring the true extent of the biological effects of back pain lifestyle-risk factors.

PURPOSE

The purpose of this study was to conduct a systematic review with multiple meta-analyses on the associations between various lifestyle factors and low back pain.

METHODS

We conducted a PRISMA systematic review and specifically included MR studies to investigate the associations between lifestyle factors-specifically, BMI, insomnia, smoking, alcohol consumption, and leisure sedentary behavior-and various back pain outcomes. Each meta-analysis synthesized data from three or more studies to assess the causal impact of these exposures on distinct back pain outcomes, including chronic pain, disability, and pain severity. Quality of studies was assessed according to STROBE-MR guidelines.

RESULTS

A total of 1576 studies were evaluated and 20 were included. Overall, the studies included were of high quality and had a low risk of bias. Our meta-analysis demonstrates the positive causal effect of BMI (OR IVW-random effects models: 1.18 [1.08-1.30]), insomnia(OR IVW-random effects models: 1.38 [1.10-1.74]), smoking(OR IVW-fixed effects models: 1.30 [1.23-1.36]), alcohol consumption(OR IVW-fixed effects models: 1.31 [1.21-1.42]) and leisure sedentary behaviors(OR IVW-random effects models: 1.52 [1.02-2.25]) on back pain.

CONCLUSION

In light of the disparate designs and causal effect estimates presented in numerous MR studies, our meta-analysis establishes a compelling argument that lifestyle-related risk factors such as BMI, insomnia, smoking, alcohol consumption, and leisure sedentary behaviors genuinely contribute to the biological development of back pain.

Lipid levels and low back pain risk: A two-sample mendelian randomization study

BACKGROUND

Previous observational studies have shown controversial results about the relationship between lipid levels and low back pain (LBP). Herein, we aimed to explore the potential causal relationship between lipid levels and LBP by using the mendelian randomization (MR) analysis.

METHODS

In this two-sample MR study, data were extracted from publicly available MRC Integrative Epidemiology Unit database. Three single-nucleotide polymorphisms (SNPs) of lipid levels [high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), and triglycerides (TG)] and two SNPs of LBP risk (LBP and back pain) were retrieved and used as genetic instrumental variables. Inverse-variance weighted (IVW), weighted median, MR-Egger, robust adjusted profile score (MR-RAPS), and MR-PRESSO were used to examine the potential causal association between lipid levels and LBP.

RESULTS

IVW (fixed effect) estimation indicated that increased HDL-C level was negatively related to the odds of LBP for European populations. [odds ratio (OR) = 0.923, 95% confidence interval (CI): 0.857-0.993, P = 0.0323]. Similar results were also found in IVW (random effect) (OR = 0.923, 95% CI: 0.866-0.983, P = 0.0134), MR-Egger (OR = 0.858, 95%CI: 0.757-0.973, P = 0.0177), MR-RAPS (OR = 0.932, 95%CI: 0.871-0.997, P = 0.0419), and MR-PRESSO (OR = 0.933, 95%CI: 0.880-0.989, P = 0.0198) analyses. Whereas no causal link was observed between LDL-C/TG and LBP risk (P>0.05).

CONCLUSION

This two-sample MR study demonstrated a causal relationship between lipid levels and LBP risk. Further investigations are necessary to elucidate the causal association and specific underlying mechanisms by which lipid levels contribute to the development of LBP.

Association between oxidative stress and chronic orofacial pain and potential druggable targets: Evidence from a Mendelian randomization study

BACKGROUND

Oxidative stress indicators affect chronic orofacial pain (COFP), but how to reduce these effects is uncertain.

OBJECTIVES

11 oxidative stress biomarkers were collected as exposures, while four forms of COFP were chosen as outcomes for Mendelian randomization (MR) study.

METHODS

The effect estimates between oxidative stress and COFP were calculated using inverse variance-weighted MR (IVW-MR). Then, functional mapping and annotation (FUMA) was utilized in order to carry out SNP-based functional enrichment analyses. In addition, the IVW-MR method was applied to combine effect estimates when using genetic variants associated with oxidative stress biomarkers as an instrument for exploring potential druggable targets.

RESULTS

The results indicated that oxidative stress biomarkers (causal OR of uric acid (UA), 0.998 for myofascial pain, 95% CI 0.996-1.000, p < .05; and OR of glutathione transferase (GST), 1.002 for dentoalveolar pain, 95% CI 1.000-1.003, p < .05) were significantly linked with the probability of COFP. Functional analysis also demonstrated that UA and myofascial pain genes were prominent in nitrogen and uracil metabolism, while GST and dentoalveolar pain genes were enriched in glutathione metabolism. Also, the study provided evidence that solute carrier family 2 member 9 (SLC2A9) and glutathione S-transferase alpha 2 (GSTA2) cause discomfort in the myofascial pain (OR = 1.003, 95% CI 1.000-1.006; p < .05) and dentoalveolar region (OR = 1.001, 95% CI 1.000-1.002; p < .05), respectively.

CONCLUSIONS

In conclusion, this MR study indicates that genetically predicted myofascial pain was significantly associated with decreased UA and dentoalveolar pain was significantly associated with increased GST level. SLC2A9 inhibitor and GSTA2 inhibitor were novel chronic orofacial pain therapies and biomarkers, but clinical trials are called to examine if these oxidative biomarkers have the protective effect against orofacial pain, and further research are needed to explore the underlying mechanisms.

Causal relationship between iron deficiency anemia and asthma: a Mendelian randomization study

Background

Observational studies have suggested an association between iron deficiency anemia (IDA) and asthma, which may affect the occurrence of asthma. However, whether IDA is a new management goal for asthma remains to be determined.

Objective

We conducted a two-sample Mendelian randomization(MR)analysis to assess the association between IDA and asthma.

Methods

We performed a two-sample MR study to assess a causal relationship between IDA (ncase = 12,434, ncontrol = 59,827) and asthma (ncase = 20,629, ncontrol = 135,449). Inverse variance weighted (IVW) was used as the primary method for the analyses. Furthermore, we used weighted medians and MR-Egger to enhance robustness. Data linking genetic variation to IDA and asthma were combined to assess the impact of IDA on asthma risk.

Results

There are five single nucleotide polymorphisms (SNPs) were used as genetic tool variables for exposure factors. Genetically determined IDA was significantly associated with an increased risk of asthma (OR = 1.37, 95% CI: 1.09-1.72, p = 0.007). There was little heterogeneity in the MR studies and no evidence of level pleiotropy was found.

Conclusions

In our MR study, our findings emphasize that IDA may be associated with a high risk of asthma, indicating a potential role for IDA in the development of asthma. Future research needs to elucidate its potential mechanisms to pave the way for the prevention and treatment of asthma.

Mendelian Randomization Reveals: Triglycerides and Sensorineural Hearing Loss

BACKGROUND

Sensorineural hearing loss (SNHL) is a multifactorial disorder with potential links to various physiological systems, including the cardiovascular system via blood lipid levels such as triglycerides (TG). This study investigates the causal relationship between TG levels and SNHL using Mendelian randomization (MR), which offers a method to reduce confounding and reverse causality by using genetic variants as instrumental variables.

METHODS

Utilizing publicly available genome-wide association study (GWAS) data, we performed a two-sample MR analysis. The initial analysis unveiled a causal relationship between TG (GWAS ID: ebi-a-GCST90018975) and SNHL (GWAS ID: finn b-H8_HL_SEN-NAS). Subsequent analysis validated this through MR with a larger sample size for TG (GWAS ID: ieu-b-111) and SNHL. To conduct the MR analysis, we utilized several methods including inverse-variance weighted (IVW), MR Egger, weighted median, and weighted mode. We also employed Cochrane's Q test to identify any heterogeneity in the MR results. To detect horizontal pleiotropy, we conducted the MR-Egger intercept test and MR pleiotropy residual sum and outliers (MR-PRESSO) test. We performed a leave-one-out analysis to assess the sensitivity of this association. Finally, a meta-analysis of the MR results was undertaken.

RESULTS

Our study found a significant positive correlation between TG and SNHL, with OR values of 1.14 (95% CI: 1.07-1.23, p < 0.001) in the IVW analysis and 1.09 (95% CI: 1.03-1.16, p < 0.006) in the replicate analysis. We also found no evidence of horizontal pleiotropy or heterogeneity between the genetic variants (p > 0.05), and a leave-one-out test confirmed the stability and robustness of this association. The meta-analysis combining the initial and replicate analyses showed a significant causal effect with OR values of 1.11 (95% CI: 1.06-1.16, p = 0.01).

CONCLUSION

These findings indicate TG as a risk factor for SNHL, suggesting potential pathways for prevention and intervention in populations at risk. This conclusion underscores the importance of managing TG levels as a strategy to mitigate the risk of developing SNHL.

Serum 25-Hydroxyvitamin D Status and Vitamin D Supplements Use Are Not Associated with Low Back Pain in the Large UK Biobank Cohort

Longitudinal studies assessing the association of vitamin D deficiency, defined by serum 25-hydroxyvitamin D levels < 30 nmol/L, and vitamin D supplement (VDS) use with low back pain (LBP) are sparse. This investigation assessed the cross-sectional and longitudinal association of vitamin D status and VDS use with LBP among 135,934 participants from the UK Biobank cohort. Approximately 21.6% of the participants had vitamin D deficiency, while only 4% regularly took VDS. In the month before study enrollment, 3.8% of the population reported experiencing LBP. An additional 3.3% of the population were diagnosed with LBP by their general practitioners for the first time during a median follow-up of 8.5 years. Vitamin D deficiency and VDS use were cross-sectionally associated with LBP in age- and sex-adjusted models, but these associations were not evident in comprehensively adjusted models. In longitudinal analyses, both vitamin D deficiency and VDS use were not associated with LBP in any model after correction for multiple testing. In conclusion, not unexpectedly due to the fact that LBP is multifactorial, our findings provide no evidence for the role of the vitamin D status in the etiology of LBP.

Vitamin D levels and five cardiovascular diseases: A Mendelian randomization study

Cardiovascular disease is the leading cause of death worldwide, whilst vitamin D levels have been found to be associated with cardiovascular disease. To investigate the causal relationship between vitamin D levels and five cardiovascular diseases, a genome-wide association study (GWAS) was carried out using data on vitamin D levels (sample size = 79366), angina pectoris (18168 cases and 187840 controls), coronary heart disease (21012 cases and 197780 controls), lacunar stroke (6030 cases and 248929 controls), heart attack (10693 cases and 451187 controls), and hypertension (55917 cases and 162837 controls), with a Mendelian randomization (MR) analysis being subsequently performed. Six single nucleotide polymorphisms were used as instrumental variables (IVs). In addition, sensitivity analysis was performed to verify the reliability of the MR results here. The results showed a causal relationship between vitamin D levels and angina pectoris (OR = 0.51, 95 % CI: 0.28-0.93, P = 0.03), coronary heart disease (OR = 0.53, 95 % CI: 0.34-0.81, P = 0.004), and lacunar stroke (OR = 0.41, 95 % CI: 0.20-0.86, P = 0.02), but no causal relationship with heart attacks (OR = 1.00, 95 % CI: 0.99-1.01, P = 0.76) or hypertension (OR = 0.99, 95 % CI: 0.73-1.34, P = 0.94). Additionally, our IVs data showed no heterogeneity or pleiotropy, whilst the results of the MR analysis were reliable. This study contributes to the prevention and treatment of these five cardiovascular diseases.

Exploring causal correlations between inflammatory cytokines and ankylosing spondylitis: a bidirectional mendelian-randomization study

Background

The impact of inflammatory factors on the development of Ankylosing Spondylitis (AS) is widely recognized, but the exact causal relationship remains unclear.

Methods

The bidirectional mendelian-randomization study utilized genetic data from a genome-wide association study (GWAS) of 186 AS cases and 456,162 controls of European ancestry. Inflammatory cytokines were obtained from a GWAS summary of 8,293 healthy participants. Causal associations were primarily investigated using the inverse variance-weighted method, supplemented by MR Egger, weighted median and weighted mode analyses. Heterogeneity in the results was assessed using the Cochrane Q test. Horizontal pleiotropy was evaluated through the MR-Egger intercept test and the MR pleiotropy residual sum and outliers (MR-PRESSO) test. Sensitivity analysis was conducted through leave-one-out analysis.

Results

The results suggest a genetically predicted potential association between beta-nerve growth factor (βNGF), Interleukin-1-beta (IL-1β), and TNF-related apoptosis inducing ligand (TRAIL) with the risk of AS (OR: 2.17, 95% CI: 1.13-4.16; OR: 0.41, 95% CI: 0.18-0.95,; OR: 1.47, 95% CI: 1.02-2.13).Additionally, Interleukin-12p70 (IL-12p70), Interleukin-17 (IL-17), Interleukin-6 (IL-6), Interleukin-4 (IL-4), Stromal-cell-derived factor 1 alpha (SDF-1α), Macrophage inflammatory protein 1β (MIP1β), Monocyte chemoattractant protein-3 (MCP-3), Platelet-derived growth factor bb (PDGFbb), Granulocyte-colony stimulating factor (GCSF), Fibroblast growth factor basic (bFGF), TNF-related apoptosis inducing ligand (TRAIL), and Interferon-gamma (IFN -γ) are suggested as consequences of AS in genetically prediction.No evidence of horizontal pleiotropy or heterogeneity between the genetic variants was found (P>0.05), and a leave-one-out test confirmed the stability and robustness of this association.

Conclusion

These findings suggest that βNGF, IL-1β, and TRAIL may play a crucial role in the pathogenesis of AS. Additionally, AS may impact the expression of cytokines such as IL-12p70, IL-17, IL-6, IL-4, SDF-1α, MIP1β, MCP-3, PDGFbb,GCSF, bFGF,TRAIL,and IFN-γ. Further investigations are warranted to determine whether these biomarkers can be utilized for the prevention or treatment of AS.