Long-Term Adverse Effects of Cigarette Smoking on the Incidence Risk of Metabolic Syndrome: Longitudinal Findings of the Korean Genome and Epidemiology Study Over 12 Years

Abstract

\n BackgroundPrevious studies have demonstrated positive associations between smoking and metabolic syndrome (MetS) in several cross-sectional studies. However, the association was not consistent in long-term studies, which makes longitudinal effects remain controversial. Thus, we investigated the association between cigarette smoking and incidence risk of MetS in a large-sample, community-based, longitudinal prospective study in both intensity and cumulative dose of cigarette smoking over 12 years of follow-up. MethodsAmong 10,038 participants, a total of 5568 men ages 40-69 years old without MetS at baseline were selected from the Korean Genome and Epidemiology Study (KoGES). The hazard ratios (HRs) and 95% confidence interval (CIs) for incident MetS were calculated using a multivariate Cox proportional-hazards regression model after adjusting for potential confounding variables and setting never smokers as the reference group for intensity (expressed as number of cigarettes per day) and duration of smoking (expressed as number of pack-years). Results Compared to the referent never smokers, the HRs (95% CIs) for incident MetS increased as the intensity of smoking in current smokers also increased: 1.50 (1.07-2.01) for 0-9 cigarettes/day, 1.66 (1.34-2.06) for 10-19 cigarettes/day, and 1.75 (1.34-2.29) for ≥20 cigarettes/day, after adjusting for age, alcohol drinking, physical activity, household income, educational level, mean arterial pressure, triglyceride, HDL-cholesterol level, and homeostasis model assessment insulin resistance. These positive relationships were similar when the cumulative dose of smoking was used in current smokers. Compared to the referent never smokers, the HRs (95% CIs) for incident MetS increased as the cumulative dose also increased: 1.63 (1.32-2.02) for <20 PYs and 1.67 (1.30-2.14) for 20 ≥PYs after adjusting for the same co-variables. ConclusionsBoth cigarette smoking intensity and cumulative dose were positively associated with MetS among community-dwelling Korean men in the large-scale, longitudinal, prospective, 12-year follow-up study.