This study aimed to investigate the association between medication adherence to oral hypoglycemic agents (OHAs) and HbA1c levels in patients with type 2 diabetes mellitus (T2DM) for more than 48 weeks, as well as the factors affecting long-term adherence to OHAs. This retrospective study included 83 patients who had been receiving OHAs for T2DM for ≥48 weeks. Medication adherence values (MAVs) were calculated using the following formula: (total prescription days - prescription days of OHAs brought at admission)/(days from the initiation of OHAs to hospitalization). We assessed the association between HbA1c and MAVs using the Jonckheere-Terpstra test. Furthermore, we examined the association between patient- and medication-related factors and MAVs affecting HbA1c levels. Based on the results, MAVs were categorized as MAV ≤0.86 and MAV >0.86, and factors affecting MAVs were analyzed. Logistic regression analysis revealed that the total number of medications, the number of nonhypoglycemic agents, and a family history of diabetes were independent determinants of MAV ≤0.86 (P < .05). Multiple regression analyses indicated that the number of dosages per day and the timing of OHA administration at lunch were independent determinants of lower MAVs (P < .05). Our findings suggest that poor medication adherence is associated with elevated HbA1c levels in T2DM patients. Independent factors contributing to poor adherence include a lower number of prescribed medications, fewer nonhypoglycemic agents, no family history, a higher daily dosage frequency, and the administration of OHAs at lunch.
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