Association of self-reported and cotinine-verified smoking status with incidence of metabolic syndrome in 47 379 Korean adults.

Abstract

The relationship of cotinine-verified vs self-reported smoking status with the incidence of metabolic syndrome (MetS) is not known. This study investigated the effect of urinary cotinine-verified vs self-reported smoking status on incident MetS. In all, 47 379 participants without MetS enrolled in the Kangbuk Samsung Health Study and Kangbuk Samsung Cohort Study between 2011 and 2012 (baseline) were included in this study and followed-up in 2014; median follow-up duration was 25 months. Cotinine-verified current smoking was defined as urinary cotinine concentrations >50 ng/mL. According to cotinine-verified smoking status at baseline and follow-up, individuals were divided into four groups: never, new, former, and sustained smokers. The incidence of MetS in the never, former, new, and sustained smoking groups was 9.9%, 19.4%, 21.4%, and 18.7%, respectively. Multivariate Cox hazard regression analyses revealed that the relative risk (RR) for incident MetS in cotinine-verified former smokers was significantly increased compared with that in cotinine-verified never smokers (RR 1.27; 95% confidence interval [CI] 1.16-1.37), especially in individuals exhibiting weight gain (≥2 kg). These results were consistent with those of self-reported smoking status. Baseline cotinine-verified current smoking (RR 1.09; 95% CI 1.03-1.15) and self-reported former (RR 1.10; 95% CI 1.02-1.18) and current (RR 1.15; 95% CI 1.07-1.23) smoking were also significantly associated with incident MetS. This large observational study showed that cotinine-verified and self-reported former smoking during follow-up increased the risk for incident MetS, especially in individuals exhibiting weight gain (≥2 kg). This suggests that weight control in former smokers would be very important to reduce the development of MetS.