Cigarette smoking is an independent risk factor for type 2 diabetes: a four-year community-based prospective study

P>Objectives We investigated the association between smoking and its additive effects with insulin resistance and beta-cell function on the incidence of type 2 diabetes in a prospective population-based cohort study. Design and method A total of 10 038 subjects were recruited from rural and urban areas. All subjects underwent 75 g oral glucose tolerance tests and full biochemical assessments at baseline and during 4-year follow-up period. The final analysis was limited to 4041 men due to the low smoking rates in women. Results The ex- and heavy current smokers had the highest incidence of diabetes of 12 center dot 5% and 11 center dot 1% respectively, compared with never-smokers (7 center dot 9%) during 4 years. After multivariate adjustment by Cox-proportional hazard model, ex- and current smokers reveal a relative risk of 1 center dot 60 (95% CI: 1 center dot 07-2 center dot 39), 2 center dot 06 (1 center dot 35-3 center dot 16, for < 20 cigarettes/day) and 2 center dot 41 (1 center dot 48-3 center dot 93, for >= 20 cigarettes/day) respectively compared with never smokers. The risk of new onset diabetes was the highest in those with low homeostasis model assessment for beta cell function (HOMA-beta) and high homeostasis model assessment for insulin resistance (HOMA-IR) group in both smokers and never smokers. Conclusions Smoking is an independent risk factor for type 2 diabetes mellitus and showed synergistic interaction with the status of low insulin secretion and high insulin resistance for developing diabetes. Given the high rates of smoking and growing burden of diabetes in the world, cessation of smoking should be considered as one of the key factors for diabetes prevention and treatment programmes.