Association between Smoking and the Switching to Insulin Therapy in Type 2 Diabetes Patients

Background: Since no studies have been published on how active smoking affects switching to insulin therapy, we aimed to investigate the role of smoking on switching to insulin therapy in type 2 diabetes mellitus patients. Methods: A total of 532 type 2 diabetes mellitus patients, who started insulin treatment due to the inability to achieve glycemic control with maximum oral anti-diabetic treatment, were included in the study. The patients were divided into three groups according to their smoking status at the beginning of insulin therapy: smokers (n = 114), ex-smokers (n = 178), and non-smokers (n = 240). Demographic and metabolic data, treatment regimens, and insulin start times were evaluated. Results: The mean age of the patients was lowest in smokers and highest in non-smokers (p = 0.021). Non-smokers' duration of diabetes (p = 0.002) and years for switching to insulin treatment after diagnosis (p < 0.000) were statistically higher than smokers. Among smokers and ex-smokers, the time to start insulin therapy was earlier in smokers. HbA1c values of non-smokers were statistically similar to the other two groups. After controlling for age, duration of diabetes, and gender, smoking status was found to have an effect on the mean time to switching to insulin therapy. Conclusions: Diabetes onset age and switching to insulin therapy is shorter in smokers than in non-smokers. These results reveal that glycemic control is impaired with smoking and patients have to switch to insulin treatment in a shorter time. Smoking cessation programs should also be offered to the diabetic population.