Stroke mortality associated with environmental tobacco smoke among never-smoking Japanese women: A prospective cohort study

Objective: This study examined the association of exposure to environmental tobacco smoke (ETS) during adulthood with stroke and its subtypes using data from a large-scale prospective cohort study in Japan. Methods: The study population included 36,021 never-smoking Japanese women who were enrolled between 1983 and 1985 and were followed-up for 15. years. We used Cox proportional hazard regression models to estimate hazard ratios (HRs) for stroke death associated with ETS exposure at home during adulthood. Results: A total of 906 cases of stroke death were observed during 437,715 person-years of follow-up. Compared with never-smoking women without smoking family members, HRs for stroke mortality among never-smoking women living with smoking family members in all subjects, in those aged 40-79. years, and in those aged ≥. 80. years were 1.14 (95% confidence interval: 0.99-1.31), 1.24 (95% CI: 1.05-1.46), and 0.89 (95% CI: 0.66-1.19), respectively, after adjustment for possible confounders. The risk was most evident for subarachnoid hemorrhage [HR: 1.66 (95% CI: 1.02-2.70) in all subjects]. Conclusion: This study suggests that exposure to ETS at home during adulthood is associated with an increased risk of stroke among never-smoking Japanese women.