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

AIMS: To assess the impact of smoking cessation on incidence of diabetes among overweight or normal-weight Japanese men. METHODS: This 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, HbA(1c) levels or being under medical treatment for diabetes. RESULTS: During 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. CONCLUSIONS: Cigarette 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.

Risk of smoking and body mass index for incidence of diabetes mellitus in a rural Japanese population.

OBJECTIVE: To assess the risk of smoking, body mass index (BMI), and both for incidence of diabetes in a rural Japanese population. METHOD: This study was a 10.1-year cohort study of 2070 men and 3802 women aged 40-69 years without diabetes at baseline who underwent a health check-up at one central hospital in Nagano Prefecture. Participants were classified according to a combination of smoking status and BMI. Participants were followed from 1990 to 2006. The incidence of diabetes was determined from fasting and random levels of plasma glucose, HbA(1c) levels or being under medical treatment for diabetes. RESULTS: Diabetes developed in 595 of the participants during 59,111 person-years of follow-up. In men, the multivariable-adjusted hazard ratios for incidence of diabetes compared with non-smokers of normal weight were as follows: 3.36 (2.02-5.60) in current smokers with normal weight and 1.70 (0.87-3.34) and 3.93 (2.22-6.96) in obese non-smokers and obese current smokers, respectively. In men the population-attributable fraction of diabetes onset due to current smoking, obesity and both were 22.0%, 2.5% and 11.2%, respectively. CONCLUSION: Regardless of BMI, smoking is an important risk factor for diabetes in male populations with a high prevalence of smoking.