Changes in treatment after the start of oral hypoglycaemic therapy in Type 2 diabetes: a population-based study

Aims: To determine the changes in oral hypoglycaemic therapy and the time to incidence of insulin therapy in people with Type 2 diabetes. Methods: A retrospective incidence cohort was constructed of 1305 subjects with Type 2 diabetes, who obtained a first prescription for oral hypoglycaemic medication between 1 July 1993 and 31 December 1994 in Tayside, Scotland. The primary endpoint of changes in oral hypoglycaemic therapy and time to insulin was determined up to the end of the follow-up, on 31 December 1995. Results: Overall, 9.4% of subjects switched to insulin, while 11% of those initially on sulphonylurea, and 6% of those initially on metformin switched to insulin therapy. Approximately three-quarters (72%) remained on the same class of drug throughout the study period (median follow-up 588 days). Only 9% died during the follow-up and this did not differ appreciably by drug group. Males were more likely to switch to insulin compared with females (10.3% vs. 8.5%), and those who switched were slightly younger with a mean age of 58 years compared with a mean age of 60 years of those who did not switch. The median time of switching to insulin was 186 days or approximately 6 months for this cohort, giving a rate of switching to insulin of 5.84% per year. Poorer glycaemic control (HBA_1c) and low body mass index (BMI) were associated with switching to insulin. Conclusions: Following initial therapy with oral hypoglycaemic medication in the population, switching to insulin occurred at a rate of 5.84% per year. Switching to insulin was associated with being younger, male, having low BMI and higher HbA_1c.