Secondhand smoke exposure predicted COPD and other tobacco-related mortality in a 17-year cohort study in China

Background: Prospective evidence on the association between secondhand smoke (SHS) and COPD and ischemic stroke is scarce. Methods: We prospectively examined the relationship between SHS and major tobacco-related deaths, particularly COPD and stroke, in 910 Chinese (439 men, 471 women) who never smoked from a 17-year follow-up study in Xi'an, China. SHS exposure was defined as exposure to another person's tobacco smoke at home or in the workplace. Results: At baseline among the 910 subjects, 44.2% were exposed to SHS at home, 52.9% in the workplace, and 67.1% at home, work, or both. From March 1, 1994, to July 1, 2011, 249 (150 men, 99 women) died within 14,016 person-years. Those who were exposed to SHS had increased mortality due to coronary heart disease (adjusted relative risk [RR], 2.15; 95% CI, 1.00-4.61), ischemic stroke (RR, 2.88; 95% CI, 1.10-7.55), lung cancer (RR, 2.00; 95% CI, 0.62-6.40), COPD (RR, 2.30; 95% CI, 1.06-5.00), and all causes (RR, 1.72; 95% CI, 1.29-2.20), with significant dose-response relationships between cumulative SHS exposure at home and work and the increased risk of cause-specific and total mortality (P for linear trend ranged from .045 to < .001). Conclusions: This study shows dose-response relationships between SHS and major tobacco-related mortality and provides new evidence to support causation for COPD and ischemic stroke.