Association between secondhand smoke exposure and new-onset hypertension in self-reported never smokers verified by cotinine

BACKGROUND/AIMS: There is no study assessing the effect of changes of secondhand smoke (SHS) exposure and new-onset hypertension. We investigated the effect of a change of SHS exposure status on new-onset hypertension in self-reported and cotinine-verified never smokers. METHODS: Out of individuals enrolled in the Kangbuk Samsung Health Study between 2011 and 2016, 87,486 self-reported and cotinine-verified never smokers without hypertension at baseline visit were included with a median follow-up of 36 months. Individuals were divided into four groups on the basis of their SHS exposure status at baseline and at follow-up: no, new, former, and sustained SHS exposure groups. RESULTS: The incidence rates per 10,000 person-year of new-onset hypertension in no, new, former, and sustained SHS exposure groups were 84.7, 113.3, 102.0, and 123.7, respectively (p < 0.001). A multivariable Cox-hazard analyses showed that new and sustained SHS exposure groups increased their hazard ratio (HR) for new-onset hypertension compared to no SHS exposure group (HR, 1.31; 95% confidence interval [CI], 1.08 to 1.60 for new SHS exposure group; and HR, 1.24; 95% CI, 1.06 to 1.45 for sustained SHS exposure group). However, being part of the former SHS exposure group did not increase the risk of new-onset hypertension (HR, 0.91; 95% CI, 0.81 to 1.03). CONCLUSIONS: This study showed that either new, or sustained SHS exposure, but not former SHS exposure, increased the risk for new-onset hypertension in self-reported never smokers verified as nonsmokers by urinary cotinine. These findings show the possibility that changing exposure to SHS even for a relatively short period can modify the risk of new-onset hypertension in self-reported and cotinine-verified never smokers.