Genetics Of Smoking And Risk Of Atherosclerotic Cardiovascular Diseases A Mendelian Randomization Study

This mendelian randomization study evaluates summary statistics from genome-wide associations involving more than 1 million individuals to assess whether there are differential associations between genetic liability to smoking and risk of coronary artery disease, peripheral artery disease, and large-artery stroke.Importance Smoking is associated with atherosclerotic cardiovascular disease, but the relative contribution to each subtype (coronary artery disease [CAD], peripheral artery disease [PAD], and large-artery stroke) remains less well understood. Objective To determine the association between genetic liability to smoking and risk of CAD, PAD, and large-artery stroke. Design, Setting, and Participants Mendelian randomization study using summary statistics from genome-wide associations of smoking (UK Biobank; up to 462 690 individuals), CAD (Coronary Artery Disease Genome Wide Replication and Meta-analysis plus the Coronary Artery Disease Genetics Consortium; up to 60 801 cases, 123 504 controls), PAD (VA Million Veteran Program; up to 24 009 cases, 150 983 controls), and large-artery stroke (MEGASTROKE; up to 4373 cases, 406 111 controls). This study was conducted using summary statistic data from large, previously described cohorts. Review of those publications does not reveal the total recruitment dates for those cohorts. Data analyses were conducted from August 2019 to June 2020. Exposures Genetic liability to smoking (as proxied by genetic variants associated with lifetime smoking index). Main Outcomes and Measures Risk (odds ratios [ORs]) of CAD, PAD, and large-artery stroke. Results Genetic liability to smoking was associated with increased risk of PAD (OR, 2.13; 95% CI, 1.78-2.56; P = 3.6 x 10(-16)), CAD (OR, 1.48; 95% CI, 1.25-1.75; P = 4.4 x 10(-6)), and stroke (OR, 1.40; 95% CI, 1.02-1.92; P = .04). Genetic liability to smoking was associated with greater risk of PAD than risk of large-artery stroke (ratio of ORs, 1.52; 95% CI, 1.05-2.19; P = .02) or CAD (ratio of ORs, 1.44; 95% CI, 1.12-1.84; P = .004). The association between genetic liability to smoking and atherosclerotic cardiovascular diseases remained independent from the effects of smoking on traditional cardiovascular risk factors. Conclusions and Relevance In this mendelian randomization analysis of data from large studies of atherosclerotic cardiovascular diseases, genetic liability to smoking was a strong risk factor for CAD, PAD, and stroke, although the estimated association was strongest between smoking and PAD. The association between smoking and atherosclerotic cardiovascular disease was independent of traditional cardiovascular risk factors.Question Are there differential associations between genetic liability to smoking and atherosclerotic cardiovascular disease (ASCVD) outcomes (coronary artery disease, peripheral artery disease, and ischemic stroke)? Findings In this mendelian randomization study including summary data for more than 1 million individuals, genetic liability to smoking was associated with increased risk of ASCVD, with the largest association with peripheral artery disease, independent from other cardiovascular risk factors. Meaning Findings of this study indicate that genetic liability to smoking has a strong, independent effect on ASCVD but is most strongly associated with peripheral artery disease; further studies of the differential effects of other ASCVD risk factors may improve risk stratification and treatment.