Smoking cessation and the incidence of pre-diabetes and type 2 diabetes: a cohort study

AimsSmoking cessation has been suggested to increase the short-term risk of type 2 diabetes mellitus (T2DM). This study aimed at assessing the association between smoking cessation and incidence of T2DM and impaired fasting glucose (IFG).MethodsData from participants in the CoLaus study, Switzerland, aged 35–75 at baseline and followed for 5.5 years were used. Participants were classified as smokers, recent (≤ 5 years), long-term (> 5 years) quitters, and non-smokers at baseline. Outcomes were IFG (fasting serum glucose (FSG) 5.6–6.99 mmol/l) and T2DM (FSG ≥ 7.0 mmol/l and/or treatment) at follow up.Results3,166 participants (63% women) had normal baseline FSG, of whom 26.7% were smokers, 6.5% recent quitters, and 23.5% long-term quitters. During follow-up 1,311 participants (41.4%) developed IFG (33.6% women, 54.7% men) and 47 (1.5%) developed T2DM (1.1% women, 2.1% men). Former smokers did not have statistically significant increased odds of IFG compared with smokers after adjustment for age, education, physical activity, hypercholesterolemia, hypertension and alcohol intake, with OR of 1.29 [95% confidence interval 0.94–1.76] for recent quitters and 1.03 [0.84–1.27] for long-term quitters. Former smokers did not have significant increased odds of T2DM compared with smokers with multivariable-adjusted OR of 1.53 [0.58–4.00] for recent quitters and 0.64 [0.27–1.48] for long-term quitters. Adjustment for body-mass index and waist circumference attenuated the association between recent quitting and IFG (OR 1.07 [0.78–1.48]) and T2DM (OR 1.28 [0.48–3.40].ConclusionIn this middle-aged population, smoking cessation was not associated with an increased risk of IFG or T2DM.