Impact of depression on utilization patterns of oral hypoglycemic agents in patients newly diagnosed with type 2 diabetes mellitus: A retrospective cohort analysis

Background: Oral hypoglycemic agents (OHAs) are an important component in the management of type 2 diabetes mellitus (DM). Large-sclae studies have demonstrated that tight glycemic control with such agents can reduce the frequency and severity of long-term DM-related complications. Objectives: The main goal of this study was to examine the impact of depression on utilization patterns of OHAs in patients newly diagnosed with type 2 DM. A secondary objective was to estimate the impact of depression on discontinuation and modification of pharmacotherapy for DM in these patients. Methods: Patients newly diagnosed with type 2 DM during a 3-year period (1998-2000) were identified from a Medicaid claims database. Presence of preexisting depression was determined on the basis of International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes. The patient cohort was followed up until they received their first prescription for an OHA (1998-2001); this date was treated as the index date for the study. Utilization patterns (ie, discontinuation, augmentation, switching, nonmodification) for OHAs were computed for a 12-month follow-up period after the index date. A multivariate framework was used to estimate the impact of depression on utilization patterns, controlling for confounders such as demographics, comorbidity, provider interaction, drug regimen complexity, and DM severity. Results: A total of 1237 newly diagnosed type 2 DM patients were identified (depressed, n=446; nondepressed, n=791). A higher number of depressed patients (23.32%) switched or augmented therapy compared with nondepressed patients (16.18%). Also, a higher fraction of depressed patients (39.46%) discontinued OHA therapy compared with nondepressed patients (32.87%). Results of a multinomial logistic regression indicated that, controlling for covariates, patients with depression were 1.72 times more likely to switch (P=0.046) and 1.89 times more likely to augment therapy (P=0.004) compared with nondepressed patients. Logistic regression analysis also indicated that, controlling for confounding covariates, patients with depression were 1.72 times more likely to modify initial OHA therapy compared with patients without depression (P=0.003). Conclusion: Depression was significantly associated with utilization patterns of OHAs in these patients newly diagnosed with type 2 DM, thus possibly affecting their disease management.