Longitudinal Adherence Patterns of Oral Antidiabetics Among Older Adults with Diabetes and Concomitant Hypertension and Hyperlipidemia Using Group-Based Trajectory Modeling

Background/Objectives: Diabetes is a prevalent chronic condition and a major contributor to morbidity, mortality, and healthcare costs in the U.S., particularly among older adults with comorbidities such as hypertension and dyslipidemia. Complex medication regimens increase the risk of nonadherence, which can worsen glycemic control, cardiovascular outcomes, and healthcare utilization. This study assessed longitudinal adherence patterns to oral antidiabetic medications among high-risk older adults and identified predictors using group-based trajectory modeling (GBTM). Methods: This retrospective cohort study used 2016–2017 Texas Medicare Advantage claims. Participants were older adults with diagnoses of diabetes, hypertension, and hyperlipidemia who had continuous plan coverage throughout the study period and at least one prescription fill for an oral antidiabetic, a statin, and a renin–angiotensin system (RAS) antagonist. Adherence was measured monthly over 12 months using the proportion of days covered (PDC). GBTM identified adherence trajectories, and multinomial logistic regression, based on the Andersen Behavioral Model, evaluated predictors using perfect adherence as the reference. Results: Among 7847 patients, three trajectories were observed: perfect adherence (59.50%), near-perfect adherence (29.21%), and rapid decline (11.29%). Female sex (OR, 1.38; 95% CI, 1.19–1.60) and absence of health plan subsidy (OR, 0.79; 95% CI, 0.68–0.92) were associated with rapid decline. Female sex (OR, 1.13; 95% CI, 1.02–1.25) and age ≥ 75 years (OR, 1.20; 95% CI, 1.00–1.43) were associated with near-perfect adherence. Conclusions: Older adults with diabetes and comorbidities exhibit distinct medication adherence patterns. Trajectory-based methods can identify those at risk for declining adherence and guide interventions to improve outcomes.