The Association Between Diabetes Metabolic Control and Drug Adherence in an Indigent Population

OBJECTIVE: Studies of the association between diabetes metabolic control and adherence to drug therapy have yielded conflicting results. Because low socioeconomic and minority populations have poorer diabetes outcomes and greater barriers to adherence, we examined the relationship between adherence and diabetes metabolic control in a large indigent population. RESEARCH DESIGN AND METHODS: The study population consisted of patients receiving medical care from a university-based internal medicine clinic serving a low-income population in rural central Virginia. The sample comprised 810 patients with type 2 diabetes who received oral diabetes medications from the clinic pharmacy and had at least one HbA(1c) determination during the study period. Multiple linear regression was used to examine the association of HbA(1c) level as well as change in HbA(1c) level with medication adherence, demographic, and clinical characteristics. RESULTS: Better metabolic control was independently associated with greater medication adherence, increasing age, white (versus African-American) race, and lower intensity of drug therapy. For each 10% increment in drug adherence, HbA(1c) decreased by 0.16% (P < 0.0001). Controlling for other demographic and clinical variables, the mean HbA(1c) of African-Americans was 0.29% higher than that of whites (P = 0.04). Additionally, the intensity of diabetes drug therapy for African-Americans was lower, as was their measured adherence to it. There was no association between metabolic control and gender, income, encounter frequency, frequency of HbA(1c) testing, or continuity of care. CONCLUSIONS: Adherence to medication regimens for type 2 diabetes is strongly associated with metabolic control in an indigent population; African-Americans have lower adherence and worse metabolic control. Greater efforts are clearly needed to facilitate diabetes self-management behaviors of low-income populations and foster culturally sensitive and appropriate care for minority groups.