Initiation of insulin therapy in elderly patients taking oral antidiabetes drugs

Abstract

Background: We sought to estimate the rate of initiation of insulin therapy among elderly patients using oral anti-diabetes drugs and to identify the factors associated with this initiation.

Methods: We conducted a population-based cohort study involving people aged 66 or more years who were newly dispensed an oral antidiabetes drug. Individuals who had received acarbose or a thiazolidinedione were excluded. The rate of insulin initiation was calculated by use of the Kaplan-Meier method. Factors associated with insulin initiation were identified by multivariable Cox regression analyses.

Results: In this cohort of 69,674 new users of oral antidiabetes drugs, insulin was initiated at rate of 9.7 cases per 1000 patient-years. Patients who had initially received an insulin secretagogue (rather than metformin), who were prescribed an oral antidiabetes drug by an endocrinologist or an internist, who received higher initial doses of an oral antidiabetes drug, who received oral corticosteroids, used glucometer strips, or were admitted to hospital in the year before initiation of oral antidiabetes therapy, or who received 16 or more medications were more likely than those without these characteristics to have insulin therapy initiated. In contrast, patients who received thiazides or who used up to 12 medications (v. none) were less likely to have insulin therapy initiated.

Interpretation: Several factors related to drugs and health services are associated with the initiation of insulin therapy in elderly patients receiving oral antidiabetes drugs. It is unclear whether these factors predict secondary failure of oral antidiabetes drugs or instead reflect better management of type 2 diabetes.

Figure 1

Selection of the study population. *Patients who received an oral antidiabetes drug between Jan. 1, 1998, and Dec. 24, 2004, and who had not taken an oral antidiabetes drug in the 1 year before the date of the first prescription.

Figure 2

Initiation of insulin among patients who started to take an oral antidiabetes drug during the study period.