Effect of Smoking Cessation on Mortality After Myocardial Infarction: Meta-analysis of Cohort Studies

OBJECTIVE: To determine the effect of smoking cessation on mortality after myocardial infarction. DATA SOURCES: English- and non-English-language articles published from 1966 through 1996 retrieved using keyword searches of MEDLINE and EMBASE supplemented by letters to authors and searching bibliographies of reviews. STUDY SELECTION: Selection of relevant abstracts and articles was performed by 2 independent reviewers. Articles were chosen that reported the results of cohort studies examining mortality in patients who quit vs continued smoking after myocardial infarction. DATA EXTRACTION: Mortality data were extracted from the selected articles by 2 independent reviewers. DATA SYNTHESIS: Twelve studies were included containing data on 5878 patients. The studies took place in 6 countries between 1949 and 1988. Duration of follow-up ranged from 2 to 10 years. All studies showed a mortality benefit associated with smoking cessation. The combined odds ratio based on a random effects model for death after myocardial infarction in those who quit smoking was 0.54 (95% confidence interval, 0.46-0.62). Relative risk reductions across studies ranged from 15% to 61%. The number needed to quit smoking to save 1 life is 13 assuming a mortality rate of 20% in continuing smokers. The mortality benefit was consistent regardless of sex, duration of follow-up, study site, and time period. CONCLUSION: Results of several cohort studies suggest that smoking cessation after myocardial infarction is associated with a significant decrease in mortality.