Smoking is significantly associated with increased risk of COVID-19 and other respiratory infections

Causal associations of physical activity and leisure sedentary behaviors with age at onset of Huntington's disease: A mendelian randomization study

BACKGROUND

Huntington's disease (HD) is a neurodegenerative disorder for which effective therapies are currently lacking. Studies suggest that increasing physical activity (PA) and reducing leisure sedentary behavior (LSB) mitigate the progression of HD, but their causal relationship with the age at onset (AAO) of HD remains uncertain. To investigate this, we conducted the Two-sample Mendelian Randomization (MR).

METHODS

Exposure were retrieved from the UK BioBank's (UKB) Genome-Wide Association Study (GWAS). PA included accelerometer-based average PA, vigorous PA, self-reported moderate-to-vigorous PA (MVPA), and light do-it-yourself activity. LSB included television (TV) time, computer time, and driving time. Outcome came from the GWAS of the GEM-HD Consortium. We applied several MR methods such as inverse variance weighted (IVW), MR-Egger regression, weighted median (WM) for sensitivity analysis.

RESULTS

Increases in light PA (β = 8.53 years, 95 % CI = 10.64 to 44.09, P = 0.001) and accelerometer-based vigorous PA (β = 5.18, 95 % CI = 0.92 to 9.43, P = 0.017) delayed AAO of HD, while longer TV time was associated with earlier AAO of HD (β = -2.88 years, 95 % CI = -4.99 to -0.77, P = 0.007). However, other PA and LSB phenotypes did not significantly affect AAO of HD.

CONCLUSION

The study revealed a unidirectional causality between PA, LSB and the AAO of HD. Increasing PA and reducing TV time delay HD onset. Therefore, we recommend increasing physical activity and reducing sedentary behavior to delay the occurrence of motor symptoms for premanifest HD individuals.

The Relationship between Smoking and Susceptibility to HIV Infection: A Two-Sample Mendelian Randomization Analysis

Smoking is prevalent among people living with the human immunodeficiency virus (HIV), and it increases morbidity and mortality in this population. However, due to ethical constraints, there is limited information on the effects of smoking on susceptibility to HIV infection. To investigate whether smoking is associated with an increased susceptibility to HIV infection, we conducted a two-sample Mendelian randomization (MR) study using summary statistics from genome-wide association studies of individuals of European ancestry who have ever smoked (n = 99,996) and have HIV (n = 412,130). The random-effects inverse-variance weighted estimation method was used as the study's primary approach, with the MR-Egger regression and the weighted-median method as complementary approaches. Using 100 single-nucleotide polymorphisms of genome-wide significance as instrumental variables for smoking, we observed a significant association between smoking and HIV infection (odds ratio 5.790, 95% confidence interval [1.785, 18.787], and p = 0.003). Comparable results were obtained using the weighted-median method. Our findings implied that smoking is probably associated with increased susceptibility to HIV infection. Given the exploratory nature of this study, further research is needed to confirm this relationship.

Associations of educational attainment with Sepsis mediated by metabolism traits and smoking: a Mendelian randomization study

Objective

Sepsis constitutes a significant global healthcare burden. Studies suggest a correlation between educational attainment and the likelihood of developing sepsis. Our goal was to utilize Mendelian randomization (MR) in order to examine the causal connection between educational achievement (EA) and sepsis, while measuring the mediating impacts of adjustable variables.

Methods

We collected statistical data summarizing educational achievement (EA), mediators, and sepsis from genome-wide association studies (GWAS). Employing a two-sample Mendelian randomization (MR) approach, we calculated the causal impact of education on sepsis. Following this, we performed multivariable MR analyses to assess the mediation proportions of various mediators, including body mass index (BMI), smoking, omega-3 fatty acids, and apolipoprotein A-I(ApoA-I).

Results

Genetic prediction of 1-SD (4.2 years) increase in educational attainment (EA) was negatively correlated with sepsis risk (OR = 0.83, 95% CI 0.71 to 0.96). Among the four identified mediators, ranked proportionally, they including BMI (38.8%), smoking (36.5%), ApoA-I (6.3%) and omega-3 (3.7%). These findings remained robust across a variety of sensitivity analyses.

Conclusion

The findings of this study provided evidence for the potential preventive impact of EA on sepsis, which may be influenced by factors including and metabolic traits and smoking. Enhancing interventions targeting these factors may contribute to reducing the burden of sepsis.

Risk phenotypes of diabetes and association with COVID-19 severity and death: an update of a living systematic review and meta-analysis

AIMS/HYPOTHESIS

To provide a systematic overview of the current body of evidence on high-risk phenotypes of diabetes associated with COVID-19 severity and death.

METHODS

This is the first update of our recently published living systematic review and meta-analysis. Observational studies investigating phenotypes in individuals with diabetes and confirmed SARS-CoV-2 infection with regard to COVID-19-related death and severity were included. The literature search was conducted from inception up to 14 February 2022 in PubMed, Epistemonikos, Web of Science and the COVID-19 Research Database and updated using PubMed alert to 1 December 2022. A random-effects meta-analysis was used to calculate summary relative risks (SRRs) with 95% CIs. The risk of bias was evaluated using the Quality in Prognosis Studies (QUIPS) tool and the certainty of evidence using the GRADE approach.

RESULTS

A total of 169 articles (147 new studies) based on approximately 900,000 individuals were included. We conducted 177 meta-analyses (83 on COVID-19-related death and 94 on COVID-19 severity). Certainty of evidence was strengthened for associations between male sex, older age, blood glucose level at admission, chronic insulin use, chronic metformin use (inversely) and pre-existing comorbidities (CVD, chronic kidney disease, chronic obstructive pulmonary disease) and COVID-19-related death. New evidence with moderate to high certainty emerged for the association between obesity (SRR [95% CI] 1.18 [1.04, 1.34], n=21 studies), HbA1c (53-75 mmol/mol [7-9%]: 1.18 [1.06, 1.32], n=8), chronic glucagon-like peptide-1 receptor agonist use (0.83 [0.71, 0.97], n=9), pre-existing heart failure (1.33 [1.21, 1.47], n=14), pre-existing liver disease (1.40 [1.17, 1.67], n=6), the Charlson index (per 1 unit increase: 1.33 [1.13, 1.57], n=2), high levels of C-reactive protein (per 5 mg/l increase: 1.07 [1.02, 1.12], n=10), aspartate aminotransferase level (per 5 U/l increase: 1.28 [1.06, 1.54], n=5), eGFR (per 10 ml/min per 1.73 m2 increase: 0.80 [0.71, 0.90], n=6), lactate dehydrogenase level (per 10 U/l increase: 1.03 [1.01, 1.04], n=7) and lymphocyte count (per 1×109/l increase: 0.59 [0.40, 0.86], n=6) and COVID-19-related death. Similar associations were observed between risk phenotypes of diabetes and severity of COVID-19, with some new evidence on existing COVID-19  vaccination status (0.32 [0.26, 0.38], n=3), pre-existing hypertension (1.23 [1.14, 1.33], n=49), neuropathy and cancer, and high IL-6 levels. A limitation of this study is that the included studies are observational in nature and residual or unmeasured confounding cannot be ruled out.

CONCLUSIONS/INTERPRETATION

Individuals with a more severe course of diabetes and pre-existing comorbidities had a poorer prognosis of COVID-19 than individuals with a milder course of the disease.

REGISTRATION

PROSPERO registration no. CRD42020193692.

PREVIOUS VERSION

This is a living systematic review and meta-analysis. The previous version can be found at https://link.springer.com/article/10.1007/s00125-021-05458-8 FUNDING: The German Diabetes Center (DDZ) is funded by the German Federal Ministry of Health and the Ministry of Culture and Science of the State North Rhine-Westphalia. This study was supported in part by a grant from the German Federal Ministry of Education and Research to the German Center for Diabetes Research (DZD).

Increased healthcare costs in COVID-19 patients with unhealthy habits: The case of smoking

INTRODUCTION

This study aims to analyze the differences in the prognosis and cost of COVID-19 patients in terms of mortality and occurrence of complications due to tobacco use.

METHODS

This study was conducted using a unique Spanish electronic database built by health professionals during the first wave of the pandemic on the admission and evolution of a patient infected by the SARS-CoV-2 virus. Data were collected on all patients admitted to La Paz hospital (Madrid) from the pandemic's beginning until 15 July 2020. Demographic factors and the incidence of complications in smoker and non-smoker patients were compared using the Mann-Whitney U-test or chi-squared test. Survival analysis was performed using the Kaplan-Meier estimator and Cox regression. Finally, the costs between the two groups were estimated using a Generalized Linear Model.

RESULTS

A total of 3521 patients were included in the analysis, with median age of 62 years (IQR: 47-78), 51.09% were women, and 16.42% were smokers. Patients who smoked had a higher incidence of complications during their hospital stay, especially complications related to the respiratory and cardiac systems. They were also associated with a worse prognosis in terms of the need for ICU admission and mortality, leading to an increase in the management cost of the smoking COVID-19 patients by 14.72%.

CONCLUSIONS

Healthcare in Spain is mainly financed by the national tax system, so introducing an additional financing system for pathologies related to the consumption of addictive substances and associated diseases and complications would decrease the burden on the economy in terms of healthcare.

Externalizing traits: Shared causalities for COVID-19 and Alzheimer's dementia using Mendelian randomization analysis

Externalizing traits have been related with the outcomes of coronavirus disease 2019 (COVID-19) and Alzheimer's dementia (AD); however, whether these associations are causal remains unknown. We used the two-sample Mendelian randomization (MR) approach with more than 200 single-nucleotide polymorphisms (SNPs) for externalizing traits to explore the causal associations of externalizing traits with the risk of COVID-19 (infected COVID-19, hospitalized COVID-19, and severe COVID-19) or AD based on the summary data. The inverse variance-weighted method (IVW) was used to estimate the main effect, followed by several sensitivity analyses. IVW analysis showed significant associations of externalizing traits with COVID-19 infection (odds ratio [OR] = 1.456, 95% confidence interval [95% CI] = 1.224-1.731), hospitalized COVID-19 (OR = 1.970, 95% CI = 1.374-2.826), and AD (OR = 1.077, 95% CI = 1.037-1.119). The results were consistent using weighted median (WM), penalized weighted median (PWM), MR-robust adjusted profile score (MR-RAPS), and leave-one-out sensitivity analyses. Our findings assist in exploring the causal effect of externalizing traits on the pathophysiology of infection and severe infection of COVID-19 and AD. Furthermore, our study provides evidence that shared externalizing traits underpin the two diseases.

Radiological Differences in COVID-19 Related Lung Manifestations Between Smokers and Non-smokers: A Single-Center Retrospective Study in Jordan

Introduction Despite the fact that smoking has been identified as a risk factor for respiratory diseases and lung infections, the relationship between smoking and coronavirus severity remains ambiguous. It is believed that smoking is a risk factor for pulmonary infections. However, the effect of smoking on COVID-19 patients is still controversial. Objective The aim of the study was to identify and analyze the distinct radiological features in COVID-19 patients with different smoking statuses. Additionally, the study sought to examine the association between smoking and the severity of pulmonary changes. Methods A retrospective cohort study of 111 patients who were referred to Al-Salt/Hussein Hospital, Al-Salt, Jordan, from January to June 2021, with a confirmed COVID-19 diagnosis and smoking status recorded. Patients' demographics, medical history, age, gender, comorbidity, and length of hospitalization were obtained from their medical records. Results Study groups were similar in median age, prevalence of chosen chronic diseases, and median length of hospital stay. Based on the median scores of the radiological findings in each lung lobe, no statistically significant differences were found between the scores and smoking status (p-values of >0.05; Mann-Whitney test). Conclusion Smoking is an independent risk factor for the severity of COVID-19. Smoking has no noticeable impact on interstitial manifestation in COVID-19 patients.

The impact of the COVID-19 pandemic on alcohol and tobacco consumption: Evidence from Peru

The COVID-19 pandemic has introduced dramatic adversities for public health around the world, especially in low and middle-income countries. While research has shown the pandemic to have direct effects on a variety of major economic and health crises, its impact on health-related behaviors is not clear. In this paper, I examine how exposure to the pandemic affects alcohol use and smoking in Peru, which experienced one of the highest COVID-related death rates albeit implementing one of the strictest lockdown policies in the world. I find that post pandemic consumption of alcohol and smoking in the last 30 days decreases by 41.3% and 44.1% respectively when compared to pre-pandemic rates. I also conclude that the intensity of engaging in these behaviors change such that the frequency of consuming alcohol in the last 30 days, binge drinking and the probability of smoking daily falls. While drinking behavior returns to pre-pandemic levels, the negative effect on smoking weakens but remains for almost two years preceding the pandemic.

Vaccine effectiveness of BNT162b2 and CoronaVac against SARS-CoV-2 omicron infection and related hospital admission among people with substance use disorder in Hong Kong: a matched case-control study

BACKGROUND

People with substance use disorder have a high risk of SARS-CoV-2 infection and subsequent poor outcomes. Few studies have evaluated COVID-19 vaccine effectiveness among people with substance use disorder. We aimed to estimate the vaccine effectiveness of BNT162b2 (Fosun-BioNTech) and CoronaVac (Sinovac) against SARS-CoV-2 omicron (B.1.1.529) infection and related hospital admission in this population.

METHODS

We did a matched case-control study using electronic health databases in Hong Kong. Individuals diagnosed with substance use disorder between Jan 1, 2016, and Jan 1, 2022, were identified. People aged 18 years and older with SARS-CoV-2 infection from Jan 1 to May 31, 2022, and people with COVID-19-related hospital admission from Feb 16 to May 31, 2022, were included as cases and were matched by age, sex, and previous clinical history with controls from all individuals diagnosed with substance use disorder who attended the Hospital Authority health services: up to three controls for SARS-CoV-2 infection and up to ten controls for hospital admission. Conditional logistical regression was used to evaluate the association between vaccination status (ie, one, two, or three doses of BNT162b2 or CoronaVac) and the risk of SARS-CoV-2 infection and COVID-19-related hospital admission, adjusted for baseline comorbidities and medication use.

FINDINGS

Among 57 674 individuals with substance use disorder, 9523 people with SARS-CoV-2 infections (mean age 61·00 years, SD 14·90; 8075 [84·8%] males and 1448 [15·2%] females) were identified and matched to 28 217 controls (mean age 60·99 years, 14·67; 24 006 [85·1%] males and 4211 [14·9%] females), and 843 people with COVID-19-related hospital admissions (mean age 70·48 years, SD 14·68; 754 [89·4%] males and 89 [10·6%] females) were identified and matched to 7459 controls (mean age 70·24 years, 13·87; 6837 [91·7%] males and 622 [8·3%] females). Data on ethnicity were not available. We observed significant vaccine effectiveness against SARS-CoV-2 infection for two-dose BNT162b2 vaccination (20·7%, 95% CI 14·0-27·0, p<0·0001) and three-dose vaccination (all BNT162b2 41·5%, 34·4-47·8, p<0·0001; all CoronaVac 13·6%, 5·4-21·0, p=0·0015; BNT162b2 booster after two-dose CoronaVac 31·3%, 19·8-41·1, p<0·0001), but not for one dose of either vaccine or two doses of CoronaVac. Significant vaccine effectiveness against COVID-19-related hospital admission was detected after one dose of BNT162b2 vaccination (35·7%, 3·8-57·1, p=0·032), two-dose vaccination (both BNT162b2 73·3%, 64·3 to 80·0, p<0·0001; both CoronaVac 59·9%, 50·2-67·7, p<0·0001), and three-dose vaccination (all BNT162b2 86·3%, 75·6-92·3, p<0·0001; all CoronaVac 73·5% 61·0-81·9, p<0·0001; BNT162b2 booster after two-dose CoronaVac 83·7%, 64·6-92·5, p<0·0001), but not after one dose of CoronaVac.

INTERPRETATION

For both BNT162b2 and CoronaVac, two-dose or three-dose vaccination was protective against COVID-19-related hospital admission and the booster dose provided protection against SARS-CoV-2 infection among people with substance use disorder. Our findings confirm the importance of booster doses in this population during the period dominated by the omicron variant.

FUNDING

Health Bureau, the Government of the Hong Kong Special Administrative Region.

Cannabis use, abuse and dependence during the COVID-19 pandemic: a scoping review

The interaction between cannabis use or addiction and SARS-COV-2 infection rates and COVID-19 outcomes is obscure. As of 08/01/2022 among 57 evaluated epidemiological/clinical studies found in Pubmed-database, most evidence for how cannabis use patterns were influenced by the pandemic was given by two systematic reviews and 17 prospective studies, mostly involving adolescents. In this age group, cannabis use patterns have not changed markedly. For adults, several cross-sectional studies reported mixed results with cannabis use having increased, decreased or remained unchanged. Two cross-sectional studies demonstrated that the severity of adults´ cannabis dependence was either increased as a consequence of increasing cannabis use during the pandemic or not changed. Regarding the effect of cannabis use on COVID-19 outcomes, we found only five retrospective/cross-sectional studies. Accordingly, (i) cannabis use did not impact mild COVID-19 symptoms; (ii) cannabis using individuals experienced more COVID-19-related hospitalizations; (iii) cannabis using veterans were associated with reduced SARS-COV-2 infection rates; (iv) frequent cannabis use was significantly associated with COVID-19 mortality, and (v) cannabis dependents were at higher risk of COVID-19 breakthrough after vaccination. It should be outlined that the validity of these retrospective/cross-sectional studies (all self-reports or register/e-health-records) is rather low. Future prospective studies on the effects of cannabis use on SARS-COV-2 infection rates and COVID-19 outcomes are clearly required for conclusive risk-benefit assessments of the role of cannabis on users' health during the pandemic. Moreover, substance dependence (including cannabis) is associated with (often untreated) somatic comorbidity, which severity is a proven key risk factor for worse COVID-19 outcomes.

Association of cannabis use disorder with cardiovascular diseases: A two-sample Mendelian randomization study

Background

The use of cannabis has increased globally due to more regions decriminalizing marijuana use for therapeutic and recreational aims. Several observational studies have revealed that cannabis use is associated with an increased risk of adverse cardiovascular pathologies and diseases. Nevertheless, the causal associations between cannabis use and cardiovascular diseases remain unclear. Hence, we performed single-variable and multivariable Mendelian randomization (MR) to evaluate the association between cannabis use disorder and various cardiovascular diseases.

Materials and methods

Summary statistics were collected from the largest-to-date genome-wide association studies (GWAS) of cannabis use disorder. The 12 SNPs for cannabis use disorder were used as instrumental variables in this study. MR estimates were pooled using a random-effects inverse-variance weighted (IVW) method. Simple median and weighted median methods were conducted as sensitivity analyses.

Results

The genetic liability to cannabis use disorder was associated with an augmented risk of coronary artery disease, myocardial infarction, atrial fibrillation, heart failure, deep venous thrombosis, pulmonary embolism, and stroke. Except for stroke, the results were inconsistent in the sensitivity analyses. The overall patterns for the associations of cannabis use disorder with atrial fibrillation, heart failure, pulmonary embolism and stroke remained in multivariable MR analyses adjusting for potential mediators, including smoking, alcohol, body mass index, blood lipid, type 2 diabetes, hypertension, and depression. However, the association with coronary artery disease, myocardial infarction, and deep venous thrombosis did not persist in multivariable MR analyses. Mediation analysis demonstrated that smoking, body mass index, low-density lipoprotein, hypertension, and depression have more significant mediation effects, which suggests that these factors partly mediate the link from cannabis use disorder to coronary artery disease, myocardial infarction, and deep venous thrombosis.

Conclusion

The genetic liability to cannabis use disorder was associated with a higher risk of atrial fibrillation, heart failure, pulmonary embolism, and stroke. The evidence for the association between cannabis use disorder, coronary artery disease, myocardial infarction, and deep venous thrombosis was weak. Hence, future use of cannabis for therapeutic and recreational aims should consider its potential impact on cardiovascular diseases.

Adherence to COVID-19 Guidelines among Current, Former, and Never Smokers

Objectives: In this paper, we explore the adherence patterns to US Centers for Disease Control and Prevention (CDC) COVID-19 mitigation guidelines among current, former, and never smokers. Methods: We used an online cross-sectional survey of adults 18 years or older in 5 northeastern states of the US (N=1084). Results: Unadjusted analyses revealed that current smokers reported lower adherence to the CDC guidelines than former smokers (27.5 vs 29.4, p<.05). After accounting for sociodemographic covariates, this finding was no longer statistically significant. However, compared to former smokers, never smokers reported wearing their mask less often (OR=0.65; 95% CI=0.45-0.94) and current smokers were less likely to report always practicing illness-related hygiene skills (OR=0.60; 95% CI=0.39-0.93).Conclusions: Never smokers had poorer adherence to CDC guidelines than former smokers, namely wearing their masks, and current smokers were less likely to always follow the hygiene recommendations. Results should inform future public health efforts in targeting current smokers with lower adherence to CDC guidelines and learning from the ability of former smokers to demonstrate high adherence.

Substance use and common contributors to morbidity: A genetics perspective

Excessive substance use and substance use disorders (SUDs) are common, serious and relapsing medical conditions. They frequently co-occur with other diseases that are leading contributors to disability worldwide. While heavy substance use may potentiate the course of some of these illnesses, there is accumulating evidence suggesting common genetic architectures. In this narrative review, we focus on four heritable medical conditions - cardiometabolic disease, chronic pain, depression and COVID-19, which are commonly overlapping with, but not necessarily a direct consequence of, SUDs. We find persuasive evidence of underlying genetic liability that predisposes to both SUDs and chronic pain, depression, and COVID-19. For cardiometabolic disease, there is greater support for a potential causal influence of problematic substance use. Our review encourages de-stigmatization of SUDs and the assessment of substance use in clinical settings. We assert that identifying shared pathways of risk has high translational potential, allowing tailoring of treatments for multiple medical conditions. FUNDING: SSR acknowledges T29KT0526, T32IR5226 and DP1DA054394; RLK acknowledges AA028292; AA acknowledges DA054869 & K02DA032573. The funders had no role in the conceptualization or writing of the paper.

The UK Biobank: A Shining Example of Genome-Wide Association Study Science with the Power to Detect the Murky Complications of Real-World Epidemiology

Genome-wide association studies (GWASs) have successfully identified thousands of genetic variants that are reliably associated with human traits. Although GWASs are restricted to certain variant frequencies, they have improved our understanding of the genetic architecture of complex traits and diseases. The UK Biobank (UKBB) has brought substantial analytical opportunity and performance to association studies. The dramatic expansion of many GWAS sample sizes afforded by the inclusion of UKBB data has improved the power of estimation of effect sizes but, critically, has done so in a context where phenotypic depth and precision enable outcome dissection and the application of epidemiological approaches. However, at the same time, the availability of such a large, well-curated, and deeply measured population-based collection has the capacity to increase our exposure to the many complications and inferential complexities associated with GWASs and other analyses. In this review, we discuss the impact that UKBB has had in the GWAS era, some of the opportunities that it brings, and exemplar challenges that illustrate the reality of using data from this world-leading resource.

The Impact of Smoking Status and Smoking-Related Comorbidities on Coronavirus Disease 2019 Patient Outcomes: A Causal Mediation Analysis

INTRODUCTION

Smoking history is a known risk factor for significant chronic diseases as well as pulmonary infections; however, the impact of smoking status on coronavirus disease 2019 (COVID-19) outcomes has not been conclusively characterized. This study aims to evaluate the association of smoking status on COVID-19 outcomes, and to explore the mechanism by which smoking and smoking-related comorbidities relate to COVID-19 outcomes.

AIMS AND METHODS

Patients admitted with SARS-CoV-2 infection from November 2020 through January 2021 were included in this study. Causal mediation models investigating the associations between smoking status and the outcomes of mortality, intensive care unit (ICU) admission, advanced respiratory support, mechanical ventilation, ICU length of stay, and hospital length of stay, through mediation via smoking-related comorbidities, were examined.

RESULTS

Active smokers did not experience worse COVID-19 outcomes once hospitalized. Former smokers had a higher odds of mortality (total effect OR 1.59, 95% CI 1.07 to 2.38, p = .01; indirect effect OR 1.45, 95% CI 1.09 to 1.93, p < .001), and advanced respiratory support (total effect OR 1.31, 95% CI 1.04 to 1.67, p = .02; indirect effect OR 1.26, 95% CI 1.03 to 1.54, p = .02), which were mediated by smoking-related comorbidities. While there was a nonsignificant increase in the total effect for mechanical ventilation, smoking-related comorbidities were significant mediators for their increased need (total effect OR 1.40, 95% CI 0.92 to 2.14, p = .13; indirect effect OR 1.47, 95% CI 1.10 to 1.87, p < .001).

CONCLUSIONS

Although active smokers did not experience worse COVID-19 outcomes compared to never smokers, these results should be interpreted with caution. Compared to never smokers, former smokers had greater odds of mortality, advanced respiratory support, and mechanical ventilation which was significantly mediated through smoking-related comorbidities.

IMPLICATIONS

Previous studies have linked smoking status with worse COVID-19 outcomes, and have inferred that smoking-related comorbidities may play a role in these findings. This causal mediation analysis provides statistical evidence supporting this hypothesis, clarifying the risk that smoking-related comorbidities impart on COVID-19 outcomes in those with a smoking history.

Identifying factors contributing to increased susceptibility to COVID-19 risk: a systematic review of Mendelian randomization studies

BACKGROUND

To summarize modifiable factors for coronavirus disease 2019 (COVID-19) suggested by Mendelian randomization studies.

METHODS

In this systematic review, we searched PubMed, EMBASE and MEDLINE, from inception to 15 November 2021, for Mendelian randomization studies in English. We selected studies that assessed associations of genetically predicted exposures with COVID-19-related outcomes (severity, hospitalization and susceptibility). Risk of bias of the included studies was evaluated based on the consideration of the three main assumptions for instrumental variable analyses.

RESULTS

We identified 700 studies through systematic search, of which 50 Mendelian randomization studies were included. Included studies have explored a wide range of socio-demographic factors, lifestyle attributes, anthropometrics and biomarkers, predisposition to diseases and druggable targets in COVID-19 risk. Mendelian randomization studies suggested that increases in smoking, obesity and inflammatory factors were associated with higher risk of COVID-19. Predisposition to ischaemic stroke, combined bipolar disorder and schizophrenia, attention-deficit and hyperactivity disorder, chronic kidney disease and idiopathic pulmonary fibrosis was potentially associated with higher COVID-19 risk. Druggable targets, such as higher protein expression of histo-blood group ABO system transferase (ABO), interleukin (IL)-6 and lower protein expression of 2'-5' oligoadenylate synthetase 1 (OAS1) were associated with higher risk of COVID-19. There was no strong genetic evidence supporting the role of vitamin D, glycaemic traits and predisposition to cardiometabolic diseases in COVID-19 risk.

CONCLUSION

This review summarizes modifiable factors for intervention (e.g. smoking, obesity and inflammatory factors) and proteomic signatures (e.g. OAS1 and IL-6) that could help identify drugs for treating COVID-19.

Appraising the causal role of smoking in multiple diseases: A systematic review and meta-analysis of Mendelian randomization studies

BACKGROUND

The causal association between cigarette smoking and several diseases remains equivocal. The purpose of this study was to appraise the causal role of smoking in a wide range of diseases by summarizing the evidence from Mendelian randomization (MR) studies.

METHODS

MR studies on genetic liability to smoking initiation or lifetime smoking (composite of smoking initiation, heaviness, duration, and cessation) in relation to circulatory system, digestive system, nervous system, musculoskeletal system, endocrine, metabolic, and eye diseases, and neoplasms published until February 15, 2022, were identified in PubMed. De novo MR analyses were performed using summary statistics data from genome-wide association studies. Meta-analysis was applied to combine study-specific estimates.

FINDINGS

Meta-analyses of findings of 29 published MR studies and 123 de novo MR analyses of 57 distinct primary outcomes showed that genetic liability to smoking (smoking initiation or lifetime smoking) was associated with increased risk of 13 circulatory system diseases, several digestive system diseases (including diverticular, gallstone, gastroesophageal reflux, and Crohn's disease, acute pancreatitis, and periodontitis), epilepsy, certain musculoskeletal system diseases (including fracture, osteoarthritis, and rheumatoid arthritis), endocrine (polycystic ovary syndrome), metabolic (type 2 diabetes) and eye diseases (including age-related macular degeneration and senile cataract) as well as cancers of the lung, head and neck, esophagus, pancreas, bladder, kidney, cervix, and ovaries, and myeloid leukemia. Smoking liability was associated with decreased risk of Parkinson's disease and prostate cancer.

INTERPRETATION

This study found robust evidence that cigarette smoking causes a wide range of diseases.

FUNDING

This work was supported by research grants from the Swedish Cancer Society (Cancerfonden), the Swedish Heart Lung Foundation (Hjärt-Lungfonden, 20210351), the Swedish Research Council for Health, Working Life and Welfare (Forte, 2018-00123), and the Swedish Research Council (Vetenskapsrådet, 2019-00977). Stephen Burgess is supported by Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (204623/Z/16/Z) and the National Institute for Health Research Cambridge Biomedical Research Centre (BRC-1215-20014). The views expressed are those of the authors and not necessarily those of the National Institute for Health Research or the Department of Health and Social Care.

Can smoking prevalence explain COVID-19 indicators (cases, mortality, and recovery)? A comparative study in OECD countries

There are many risk factors associated with the spread of the COVID-19 pandemic, including low wind speed, fossil fuel energy production, air pollution, and smoking. Several studies argue that smoking is not a risk factor for COVID-19 morbidity among males or any other sub-group. The study aims to analyze the following research questions: (1) can smoking prevalence explain COVID-19 indicators (cases, mortality, and recovery)? Are these relationships monotonically increasing or decreasing? In an attempt to test the counter-intuitive possibility of a non-linear relationship, the proposed empirical model relaxes the assumption of monotonic change by applying the quadratic design and testing which one of the two competing models (quadratic or linear) better fits the data. Findings suggest more complex relationships between corona indices and prevalence of smoking than previously thought. These patterns might be explained by several conditions such as the attenuation of hypercytokinemia for mild levels of smoking prevalence compared with non-smokers, elevated social distancing of smokers in countries with lower smoking prevalence, and unidentified factors that should be examined in future research.

Cancers and COVID-19 Risk: A Mendelian Randomization Study

Simple Summary

During the COVID-19 pandemic, cancer patients are regarded as a highly vulnerable population. Given the unavoidable bias and unmeasured confounders in observational studies, the causal effects of cancers on COVID-19 outcomes are largely unknown. In the study, we tried to evaluate the causal effects of cancers on COVID-19 outcomes using the Mendelian randomization (MR) approach. No strong evidence was observed to support a causal role of cancer in COVID-19 development. Previous observational correlations between cancers and COVID-19 outcomes were likely confounded. Large and well-conducted epidemiological studies are required to determine whether cancers causally contribute to increased risk of COVID-19.

Abstract

Observational studies have shown increased COVID-19 risk among cancer patients, but the causality has not been proven yet. Mendelian randomization analysis can use the genetic variants, independently of confounders, to obtain causal estimates which are considerably less confounded. We aimed to investigate the causal associations of cancers with COVID-19 outcomes using the MR analysis. The inverse-variance weighted (IVW) method was employed as the primary analysis. Sensitivity analyses and multivariable MR analyses were conducted. Notably, IVW analysis of univariable MR revealed that overall cancer and twelve site-specific cancers had no causal association with COVID-19 severity, hospitalization or susceptibility. The corresponding p-values for the casual associations were all statistically insignificant: overall cancer (p = 0.34; p = 0.42; p = 0.69), lung cancer (p = 0.60; p = 0.37; p = 0.96), breast cancer (p = 0.43; p = 0.74; p = 0.43), endometrial cancer (p = 0.79; p = 0.24; p = 0.83), prostate cancer (p = 0.54; p = 0.17; p = 0.58), thyroid cancer (p = 0.70; p = 0.80; p = 0.28), ovarian cancer (p = 0.62; p = 0.96; p = 0.93), melanoma (p = 0.79; p = 0.45; p = 0.82), small bowel cancer (p = 0.09; p = 0.08; p = 0.19), colorectal cancer (p = 0.85; p = 0.79; p = 0.30), oropharyngeal cancer (p = 0.31; not applicable, NA; p = 0.80), lymphoma (p = 0.51; NA; p = 0.37) and cervical cancer (p = 0.25; p = 0.32; p = 0.68). Sensitivity analyses and multivariable MR analyses yielded similar results. In conclusion, cancers might have no causal effect on increasing COVID-19 risk. Further large-scale population studies are needed to validate our findings.