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

BACKGROUND: No study has reported the relationship of cotinine-verified vs. self-reported smoking status with incidence of metabolic syndrome (MetS). The aim of this study is to determine the effect of urinary cotinine-verified vs. self-reported smoking status on incident metabolic syndrome.

METHODS: A total of 47,379 participants without MetS who visited between 2011 and 2012 at baseline were included and followed up at 2014. Median follow-up duration was 25 months. Cotinine-verified current smoking was defined as urinary cotinine level of above 50 ng/mL. According to their cotinine-verified smoking status at baseline and at follow-up, individuals were divided into four groups: never, new, former, and sustained smoking.

RESULTS: Incidences of MetS in never, former, new, and sustained smoking groups were 9.9%, 19.4%, 21.4%, and 18.7%, respectively. Multivariate Cox hazard regression analyses for the four groups revealed that the relative risk (RR) for incident MetS in cotinine-verified former smoking group was significantly increased compared to that in cotinine-verified never smoking group (RR[95% CI], 1.27[1.16, 1.37]), especially in the individuals with weight gain (≥2kg). These results were consistent with those of self-reported smoking groups. Baseline cotinine-verified current smoking (1.09[1.03, 1.15]) and self-reported former (1.10[1.02, 1.18]) and current (1.15[1.07, 1.23]) smoking were also significantly associated with incident MetS.

CONCLUSIONS: 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 with weight gain (≥2kg). This finding suggests that weight control in former smokers would be very important to reduce the development of MetS.