Tobacco smoking and the risk of heart failure: A systematic review and meta-analysis of prospective studies.

Background We conducted a systematic review and meta-analysis to clarify the association between smoking and the risk of developing heart failure. Methods PubMed and Embase databases were searched up to 24 July 2018. Prospective studies were included if they reported adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) of heart failure associated with smoking. Summary RRs and 95% CIs were estimated using a random effects model. Results Twenty-six studies were included. The summary RR was 1.75 (95% CI: 1.54-1.99, I2 = 81%, n = 10) for current smokers, 1.16 (95% CI: 1.08-1.24, I2 = 51%, n = 9) for former smokers, and 1.44 (1.34-1.55, I2 = 83%, n = 10) for ever smokers compared with never smokers. The summary RR was 1.41 (95% CI: 1.01-1.96, I2 = 82%, n = 2) per 10 cigarettes per day, 1.11 (95% CI: 1.04-1.18, I2 = 70%, n = 3) and 1.08 (95% CI: 1.02-1.14, I2 = 34%, n = 2) per 10 pack-years among ever smokers and former smokers, respectively, and 0.79 (95% CI: 0.63-1.00, I2 = 96%, n = 2) per 10 years since quitting smoking. The association between smoking cessation and heart failure reached significance at 15 years of smoking cessation, and at 30 years the summary RR was 0.72 (95% CI: 0.57-0.90), only slightly higher than the summary RR for never smokers (0.64 (95% CI: 0.57-0.72)) when compared with current smokers. Conclusion Smoking is associated with increased risk of heart failure, but the risk decreases with increasing duration since smoking cessation. Any further studies should investigate the association between number of cigarettes per day, duration, pack-years and time since quitting smoking and risk of heart failure.