Smoking status and risk for recurrent coronary events after myocardial infarction

Background: Questions remain about the importance of smoking and smoking cessation after incident myocardial infarction. Objective: To assess the association between smoking status and risk for recurrent coronary events. Design: Retrospective, population-based, inception cohort study. Setting: Health maintenance organization from 1986 to 1996. Patients: 2619 persons who survived to hospital discharge after a first myocardial infarction. Measurements: Relative risk (RR), assessed by using Cox proportional hazards regression analysis, for recurrent coronary events in nonsmokers (persons with no history of smoking), former smokers (persons who had stopped smoking before infarction), quitters (persons who stopped smoking after infarction), and active smokers (persons who continued smoking after infarction). Results: At the time of incident infarction, 33.6% of patients were nonsmokers, 35.5% were former smokers, and 30.9% were active smokers. Of the 808 persons who were active smokers at the time of incident infarction, 449 quit smoking during hospitalization or after discharge. With nonsmokers as the reference group, the multivariable RR for recurrent coronary events (n = 433) was 1.17 (95% CI, 0.93 to 1.43) for former smokers and 1.51 (CI, 1.10 to 2.07) for active smokers. Among quitters, the RR decreased as duration of cessation increased: With nonsmokers as the reference group, the RR for quitters was 1.62 (CI, 1.02 to 2.61) if the duration of cessation was 0 to less than 6 months, 1.60 (CI, 0.97 to 2.60) if the duration was 6 to less than 18 months, 1.48 (CI, 0.76 to 2.51) if the duration was 18 to less than 36 months, and 1.02 (CI, 0.54 to 1.86) if the duration was 36 months or more (P = 0.01 for trend). Conclusion: After incident myocardial infarction, smoking was associated with an elevated risk for recurrent coronary events. In persons who quit smoking after infarction, the risk declined to equal that of nonsmokers by 3 years after cessation.