Association between passive smoking and cardiovascular disease: A systematic review and meta-analysis

Background The association between passive smoking (PS) and cardiovascular disease (CVD) has not yet been fully clarified. Objective This meta-analysis was performed to evaluate the association between PS and the incidence of CVDs and mortality due to CVD. Methods PubMed/Medicine, Science Direct, Scopus, Web of Knowledge, and ProQuest were searched to identify observational studies that met the inclusion criteria without time, language, age, gender, ethnicity, and design restrictions until July 30, 2018. In case-control studies, relative risk (RR) with 95% confidence interval (CI) was calculated for the relationship between PS and CVD incidence. Also, in cohort studies, hazard ratio (HR) with 95% CI was calculated for the relationship between PS and CVD mortality. Results Eighteen studies (10 cohort and 8 case-control studies) were included with 10,672 participants (2,542 cases and 8,130 controls) in case-control studies and 2,313,935 participants in cohort studies. This meta-analysis in case-control studies revealed that the PS could increase the risk of CVD incidence by 28% (adjusted RR = 1.28 [95% CI 1.09, 1.50]), where the highest risk was associated with those who were exposed to second-hand smoke at home and at work (Adjusted RR = 1.41 [95% CI 0.73, 2.70]). Also, the meta-analysis in cohort studies indicated that PS was associated with a 12% higher increase in the risk of CVD mortality (Adjusted HR = 1.12 [95% CI 1.06, 1.20]) with the highest risk of mortality being observed for those who were exposed to second-hand smoking at home, work, and public places (Adjusted HR = 1.26 [95% CI 1.13, 1.40]). Conclusions PS is significantly associated with an increased risk of incidence and mortality of CVD.