Association between Secondhand Smoke Exposure and Hypertension in 106,268 Korean Self-Reported Never-Smokers Verified by Cotinine

No study has reported the relationship between secondhand smoke (SHS) exposure and hypertension in self-reported never-smokers verified by nicotine metabolite. The aim of this study is to determine the relationship between SHS exposure and hypertension in self-reported and cotinine-verified never-smokers. A total of 106,268 self-reported never-smokers, verified as nonsmokers by urinary cotinine, who participated in Kangbuk Samsung Cohort study (KSCS) between 2012 and 2016 were included. Cotinine-verified nonsmokers were defined as individuals having urinary cotinine <50 ng/mL. SHS exposure was defined as current exposure to passive smoke indoors at home or the workplace. The multivariate regression model revealed that SHS exposure was associated with hypertension (odds ratio (OR) (95% confidence interval (CI)), 1.16 (1.08, 1.24)). Current SHS exposure that has been exposed to home SHS (1.22 (1.11, 1.33)) as well as current SHS exposure only at the workplace (1.15 (1.02, 1.29)) significantly increased the ORs for hypertension compared to no SHS exposure. There was no significant gender interaction for the relationships between SHS exposure and hypertension. This study showed that SHS exposure was significantly associated with hypertension in self-reported never-smokers verified as nonsmokers by urinary cotinine, suggesting necessity of health program and stricter smoking regulation to reduce the risk of hypertension.