Tobacco smoking and the risk of abdominal aortic aneurysm: a systematic review and meta-analysis of prospective studies

Several studies have found that smoking increases the risk of abdominal aortic aneurysm, however, the strength of the association has differed between studies and data from cohort studies have not yet been summarized. A systematic review and meta-analysis was therefore conducted to clarify this association. We searched PubMed and Embase databases up to May 2^nd 2018. A random effects model was used to estimate summary relative risks (RRs) and 95% confidence intervals (CIs). Twenty three prospective studies were included. Comparing current, former and ever smokers with never smokers the summary RRs were 4.87 (95% CI: 3.93-6.02, I² = 92%, n = 20), 2.10 (95% CI: 1.76-2.50, I² = 71%, n = 15) and 3.28 (95% CI: 2.60-4.15, I² = 96%, n = 18), respectively. The summary RR was 1.87 (95% CI: 1.45-2.40, I² = 97%) per 10 cigarettes per day, 1.78 (95% CI: 1.54-2.06, I² = 83%) per 10 pack-years was and 0.45 (95% CI: 0.32-0.63, I² = 92.3%) per 10 years of smoking cessation. There was evidence of nonlinearity for cigarettes per day and pack-years (p_nonlinearity < 0.0001 and p_nonlinearity = 0.02, respectively), but not for smoking cessation, p_nonlinearity = 0.85. Among smokers who quit, the RR was similar to that of never smokers by 25 years of smoking cessation. These findings confirm a strong association between smoking and the risk of developing abdominal aortic aneurysms.