Effect of smoking on hemoglobin A1c and body mass index in patients with type 2 diabetes mellitus

Background: Smoking is associated with a decrease in body weight in patients without diabetes mellitus and an increase in insulin resistance and hemoglobin A(1c) (HbA(1c)) levels in patients with type 1 diabetes mellitus. Whether smoking is associated with an increase in HbA(1c) and/or a decrease in body mass index (BMI) in type 2 diabetes mellitus is unresolved, however. Therefore, the objective of this study was to determine the effect of smoking on HbA(1c) levels and BMI in a cross-section of outpatients with type 2 diabetes mellitus. Methods: A questionnaire was completed by 102 sequential outpatients (32 men, 70 women) with type 2 diabetes mellitus to assess age, sex, duration of diabetes mellitus, medications, exposure to nicotine, medical complications as a result of type 2 diabetes mellitus, and BMI. In addition, a urine sample was obtained from each patient to assess the microalbumin-creatinine and cotinine-creatinine ratios. RbA, level were also obtained from each volunteer as a measure of glucose control. Results: Smokers had significantly higher cotinine-creatinine ratios than nonsmokers. Smokers and nonsmokers did not differ significantly with regard to HbA, level, BMI, or duration of diabetes mellitus. Smokers were younger than nonsmokers. Smokers and nonsmokers did not differ significantly in terms of microalbumin-creatinine ratio, amount of diabetic medications, or medical complications. Conclusion: The results of this study suggest that smoking does not have a significant direct effect on BMI or HbA, in patients with type 2 diabetes mellitus. This conclusion suggests that the relationship between these factors is much more complex than in people without diabetes or in patients with type 1 diabetes mellitus.