Impact of Polypharmacy on Medication Adherence in Patients with Comorbid Type 2 Diabetes and Hypertension in Tanzania: A Cross-Sectional Study

Background: Diabetes mellitus and hypertension are increasingly prevalent non-communicable diseases that often coexist due to their interrelated pathophysiology and commonalities of risk factors. Effective management of these two comorbid conditions often involves polypharmacy, defined as the concurrent use of five or more medications, which for therapeutically relevant outcomes requires a high-medication adherence. Limited data exist on the extent of polypharmacy and its impact on adherence among Tanzanian patients with these comorbidities. This study therefore aimed at evaluating the prevalence of polypharmacy and its impact on medication adherence levels among this population. Methodology: A cross-sectional study involving 396 outpatients was conducted at Muhimbili National Hospital. Consecutive sampling was used to recruit eligible participants. Data was collected using structured-questionnaire which captured information on socio-demographics, clinical characteristics and adherence behaviors. Polypharmacy was defined as using five or more medications. Medication adherence was assessed using the Medication Adherence Report Scale (MARS-5). Multivariable logistic regression was performed to identify factors associated with adherence. Results: 71% of the study participants were on five or more medications, indicating high polypharmacy prevalence, with a median of six medications. Medication adherence was reported at 55.1%. Factors associated with lower adherence included moderate (APR: 0.83, P = 0.001) and high fasting glucose (APR: 0.66, P < 0.001), herbal medicine use (APR: 0.72, P < 0.001), and uncontrolled blood pressure. Conclusion: This study reveals a high prevalence of polypharmacy with moderate medication adherence among patients with comorbid T2DM and hypertension. These findings suggest a targeted intervention utilizing such as patient education and medication reviews are essential to improve adherence and management in Tanzania.