Association of environmental tobacco smoke exposure with metabolic syndrome: A longitudinal Cohort Study of 71,055 never smokers

Abstract

Background and aimsEffects of environmental tobacco smoke (ETS) exposure and a change in ETS exposure status on metabolic syndrome (MetS) remain unknown. Thus, the aim of this study was to evaluate the effect of ETS exposure on MetS in self-reported and cotinine-validated never smokers. Methods and resultsFrom a large longitudinal cohort study, 71,055 cotinine-validated never smokers without MetS at baseline were included. These participants were divided into four groups (no, new, former, and continuous ETS exposure groups) based on their ETS exposure status at baseline and follow-up. The association between ETS exposure and MetS was assessed using multivariable Cox hazard regression analyses.During a median follow-up of 33 months, 15.0 cases/10,000 person-years (PY) developed MetS. Incidence rates per 10,000 PY of MetS in no, new, former, and continuous ETS exposure groups were 14.0, 18.5, 16.5, and 19.0, respectively. In multivariable Cox hazard regression analyses, the new and continuous ETS exposure groups showed increased risk of MetS compared to the no ETS exposure group (hazard ratio [95% confidence interval]: 1.35 [1.16, 1.56], p-value < 0.001 for the new ETS exposure group and 1.19 [1.06, 1.34], p-value = 0.004 for the continuous ETS exposure group). However, the former ETS exposure group did not show an increased risk of MetS (0.96 [0.88, 1.05], p-value = 0.36). ConclusionThis study showed that ETS exposure and changes in ETS exposure status over approximately three years could modify the risk of MetS, suggesting that avoidance of ETS may not increase the risk of incidence of MetS.