Smoking habits and the risk of type 2 diabetes: a case-control study

The objective of the study was to assess the relationship between smoking and the risk of type 2 diabetes.

This case-control study included 234 cases with newly confirmed diagnoses of type 2 diabetes and 468 controls who were free of the disease in 2001. Cases and controls were matched by gender and age (+/-5 years). A questionnaire was used to collect information on the possible risk factors of type 2 diabetes. Clinical measurements were taken in accordance with the recommendations of the WHO. Fasting plasma glucose and triglycerides were also measured, and the glucose tolerance test was performed in the controls. The odds ratios (OR) and 95% confidence intervals (CI) for type 2 diabetes were calculated using conditional logistic regression.

The diabetes cases had significantly less education, more first-degree relatives with a positive family history of diabetes and higher body mass index (BMI) scores compared with the controls. Also, after adjusting for possible confounders, an increased risk of type 2 diabetes was determined for current smokers (OR=2.41; 95% CI 1.07-5.44) vs. non-smokers. In addition, there was an association between the disease and duration of smoking (OR=2.47; 95% CI 1.03-5.93 for 40 years or more) vs. non-smokers, and those who had been smokers for 10 or more pack-years had twice the risk of diabetes (OR=2.17; 95% CI 1.07-4.40) vs. non-smokers. There were no significant associations found between the risk of type 2 diabetes and number of cigarettes smoked per day or stopping smoking.

Our data confirms that smoking may be an independent risk factor for type 2 diabetes.