Current smoking status as a predictor of cerebral infarction in men: a retrospective cohort study in South Korea

OBJECTIVES: We examined the relationship between duration (pack-year) of smoking and the risk of developing cerebral infarction in Korean men. DESIGN: Retrospective cohort study. SETTING: National Health Insurance Service-National Sample Cohort in Korea. PARTICIPANTS: Of 125 743 male participants from the National Health Insurance System undergoing medical health check-up in 2009, 114 377 were included in the final analysis. PRIMARY AND SECONDARY OUTCOME MEASURES: Development of cerebral infarction according to smoking duration after adjusting for age, body mass index, systolic blood pressure, fasting blood glucose, total cholesterol, γ-glutamyltransferase, estimated glomerular filtration rate, alcohol intake and physical activity. RESULTS: During 495 827.3 person-years of follow-up, 1450 incident cases of cerebral infarction developed between 2009 and 2013. The multivariate adjusted HRs (95% CI) for cerebral infarction between groups 2, 3 and 4 by duration of smoking were 1.02 (0.88 to 1.19), 1.36 (1.19 to 1.56) and 1.49 (1.28 to 1.74), respectively. In our secondary analysis by smoking status, the HR (95% CI) of former smokers showed a significant relationship in the unadjusted model but did not show statistically significant associations in the multivariate adjusted model. The HR (95% CI) of current smokers showed significant relationship in both the unadjusted and multivariate adjusted models (p for trend <0.001). CONCLUSIONS: The study indicates that the prolonged duration of smoking (pack-year) increases the risk of cerebral infarction. Current smoking poses a higher risk for the development of cerebral infraction than former smoking among Korean men, indicating that current smoking cessation would be more protective.