Anti-Hyperglycemic Medication Adherence and Health Services Utilization in People with Diabetes: A Longitudinal Study of Alberta’s Tomorrow Project

Background: Little is known about the long-term (>2 years) relationship between the time-varying drug adherence and healthcare utilization for patients with diabetes. Objective: To characterize the relationship between time-varying anti-hyperglycemic medication adherence and healthcare utilization in patients with diabetes, using data from Alberta's Tomorrow Project, a population-based cohort study in Alberta, Canada. Methods: Incident cases of diabetes with at least 24 months of follow-up were included in the study. Anti-hyperglycemic drug adherence was measured by proportion of days covered (PDC) in the past 12 months for each year after diagnosis. The rate of healthcare utilization was assessed for the subsequent 12 months, 36 months and 60 months. A time-varying, negative binomial generalized estimating equation model was used to examine the association between medication adherence and healthcare utilization. Results: Among 2155 incident cases of diabetes, average age at diagnosis was 59.6[+ or -]9.3, 51.0% were female and average duration of follow-up was 7.3[+ or -]3.7 (range, 2.0-16.2) years. The proportion of patients taking anti-hyperglycemic medications was 47.6% during the first year of diagnosis, which increased to 77.3% by the end of follow-up. Compared to adherent patients (PDC [greater than or equal to]0.8), non-adherent patients (PDC