Impact of smoking cessation on incidence of diabetes mellitus among overweight or normal-weight Japanese men

AimsTo assess the impact of smoking cessation on incidence of diabetes among overweight or normal-weight Japanese men.MethodsThis 9.2-year cohort study included 2070 men aged 40–69 years without diabetes. We classified them according to smoking status as non-smokers, past smokers (>9, 6–9, 3–5 and <3 years) and current smokers. Participants were followed up until diabetes developed or the end of 2006. The incidence of diabetes was determined from fasting and random plasma glucose levels, HbA1c levels or being under medical treatment for diabetes.ResultsDuring 18,963 person-years of follow-up, 246 of the participants developed diabetes. The risk for diabetes peaked within 3 years of quitting (HR: 2.98, 95% CI: 1.38–6.27) and persisted at 5 years after quitting smoking (HR, 2.49; 95% CI, 1.18–5.26) among overweight individuals. Moreover, this study identified a high risk for diabetes among past smokers who had quit >9 years in both normal weight and overweight.ConclusionsCigarette smoking predicts incidence of diabetes, but smoking cessation leads to higher short-term risk in overweight and long-term risk in both. Preventing smoking is superior to smoking cessation, and is very important for avoiding diabetes.