Medication Adherence and Associated Hemoglobin A1c in Type 2 Diabetes

BACKGROUND: Tight blood glucose control has been correlated with a reduction in diabetes complications. Adherence to antidiabetic medications is crucial to achieving blood glucose control. OBJECTIVE: To assess the relationship between good glucose control [glycosylated hemoglobin (HbA1c) levels] and adherence to prescribed treatment in patients on a stable medication regimen for type 2 diabetes. METHODS: The Morisky survey, a 4–item questionnaire that predicts patient medication-taking behavior, was used to assess adherence in 301 patients. The relationship of HbA1c to Morisky score was evaluated, controlling for other variables related to patient demographics and clinical characteristics. Data were analyzed using a general linear model on log (HbA1c). RESULTS: Unadjusted mean HbA1c values (capped at 14.0%) for patients with Morisky scores of 0 or 1, 2, 3, and 4 were 8.92%, 8.67%, 7.74%, and 7.60%, respectively. Of all patients, 13.0%, 14.0%, 24.3%, and 48.8% had scores of 0 or 1, 2, 3, and 4, respectively. Good adherence (Morisky score ≥3) was associated with a 10% lower total HbA1c (p = 0.0003) adjusted for all other factors in the model. Duration of diabetes (5–10 y) and presence of diabetes complications were also significantly associated with HbA1c (p = 0.026 and 0.002, respectively). Adherence was poor in 27% of patients. CONCLUSIONS: This study found that patients with a higher score on the Morisky scale had a lower associated HbA1c measurement. The Morisky score may be an efficient tool for identifying patients with poor medication-taking behavior who can then be targeted for directed adherence counseling services.