Smoking and development of type 2 diabetes in patients with decreased functional capacity

Data regarding the possible contribution of cigarette smoking to development of type 2 diabetes are scarce and inconclusive. Patients with impaired functional capacity and diminished physical activity are prone to develop new diabetes. However, the role of smoking on diabetes incidence among these patients has not been specifically investigated. The present study was aimed to evaluate the association between cigarette smoking and development of type 2 diabetes in patients with coronary artery disease and decreased functional capacity over a 6.2-year follow-up period.

The study sample comprised 630 nondiabetic patients aged 45-74 years, with a fasting blood glucose of <126 mg/dl and with impaired functional capacity (New York Heart Association functional class II and III). The sample was classified into two groups: 1) non smokers (never and past smokers pooled together)--552 patients and 2) current smokers--78 patients.

Smokers were younger but they had a relatively unfavorable lipid profile (with respect to apolipoproteins A, triglyceride and HDL-cholesterol levels). No significant differences between the groups were found for weight, body mass index, total cholesterol and blood pressure. During the follow-up, development of new diabetes was recorded in 98 patients: in 80 (14.5%) non smokers and in 18 (23.1%) smokers, p=0.05. Among the non smokers, there were no significant differences in diabetes incidence between 357 past smokers and 195 never smokers: respectively, 48 (13.4%) and 32 (16.4%), p=0.34. In addition, all-cause mortality among the smokers (23.1%) was significantly higher than in non smokers (12.7%), p=0.01. Multivariate analysis identified current smoking as an independent predictor of increased risk of new diabetes development with a hazard ratio of 1.94 (95% confidence interval 1.16-3.25).

Current smoking was associated with an independent two-fold increased risk for development of type 2 diabetes in patients with impaired functional capacity.