Abstract
AIMS/INTRODUCTION: To assess the impact of smoking on impaired insulin secretion and insulin resistance in Japanese men. MATERIALS AND METHODS: This study included 1,199 men aged 30-79 years without diabetes, impaired insulin secretion and insulin resistance at baseline who underwent a comprehensive medical check-up between April 2006 and March 2007 at Saku Central Hospital. Smoking status was categorized as current, ex-smoker and never-smoker. Insulinogenic index and homeostasis model assessment-insulin resistance were determined using a standard 75-g oral glucose tolerance test. The Japan Diabetes Society criteria were used to define impaired insulin secretion and insulin resistance. Participants were followed up until March 2011. RESULTS: A total of 449 and 99 men developed impaired insulin secretion and insulin resistance during 3,403 and 4,092 person-years follow up, respectively. The multivariable-adjusted hazard ratios (HRs) for impaired insulin secretion were 1.06 (95% confidence interval [CI] 0.84-1.33) in ex-smokers and 1.95 (95% CI 1.44-2.63) in current smokers compared with never-smokers after adjustment for age, familial history of diabetes, alcohol consumption, exercise, systolic blood pressure, triglyceride, γ-glutamyltransferase, waist circumference, leukocyte count, changes in smoking status and changes in waist circumference. The number of pack-years was positively associated with the risk for impaired insulin secretion in a dose-dependent manner (P-values for trend <0.001). The multivariable-adjusted HRs for insulin resistance were 0.95 (95% CI 0.56-1.61) in ex-smokers and 1.11 (95% CI 0.67-1.79) in current smokers compared with never-smokers. CONCLUSIONS: Cigarette smoking is a modifiable risk factor for impaired insulin secretion. The findings might also be important for other Asian populations, which have low insulin secreting ability.