Cigarette Smoking as a Risk Factor for Coronary Heart Disease in Women Compared With Men: A Systematic Review and Meta-Analysis of Prospective Cohort Studies
What is the effect of smoking on coronary heart disease (CHD) in women compared with men after accounting for sex differences in other major risk factors?
The investigators undertook a systematic review and meta-analysis of prospective cohort studies published between January 1, 1966, and December 31, 2010, from four online databases. They selected cohort studies that were stratified by sex with measures of relative risk (RR), and associated variability, for CHD and current smoking compared with not smoking. The investigators pooled data with a random-effects model with inverse variance weighting, and estimated RR ratios (RRRs) between men and women.
The investigators reviewed 8,005 abstracts and included 26 articles with data for 3,912,809 individuals and 67,075 CHD events from 86 prospective trials. In 75 cohorts (2.4 million participants) that adjusted for cardiovascular risk factors other than CHD, the pooled adjusted female-to-male RRR of smoking compared with not smoking for CHD was 1.25 (95% confidence interval, 1.12-1.39; p < 0.0001). This outcome was unchanged after adjustment for potential publication bias, and there was no evidence of important between-study heterogeneity (p = 0.21). The RRR increased by 2% for every additional year of study follow-up (p = 0.03). In pooled data from 53 studies, there was no evidence of a sex difference in the RR between participants who had previously smoked compared with those who never had (RRR, 0.96; 95% CI, 0.86-1.08; p = 0.53).
The authors concluded that whether mechanisms underlying the sex difference in risk of CHD are biological or related to differences in smoking behavior between men and women is unclear.
This review of data from more than 2.4 million people and more than 44,000 CHD events suggests that, compared with nonsmokers, women who smoke may have a 25% greater RR of CHD than do male smokers, independent of other cardiovascular risk factors. Most of the studies included in this analysis reported higher, not lower, RRs of CHD in female smokers than in male smokers. Physicians, health professionals, and society should increase their efforts at promotion of smoking cessation in all individuals, whether male or female. Given the present trends in female smoking, inclusion of a female perspective in smoking cessation programs and policies is going to be crucial from a public health perspective.
Keywords: Follow-Up Studies, Coronary Disease, Risk Factors, Tobacco Use Disorder, Smoking Cessation, Smoking
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