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BACKGROUND: Chronically ill patients often experience difficulty paying for their medications and, as a result, use less than prescribed. OBJECTIVES: The objectives of this study were to determine the relationship between patients with diabetes' health insurance coverage and cost-related medication underuse, the association between cost-related underuse and health outcomes, and the role of comorbidity in this process. RESEARCH DESIGN: We used a patient survey with linkage to insurance information and hemoglobin A1C (A1C) test results. PATIENTS: We studied 766 adults with diabetes recruited from 3 Veterans Affairs (VA), 1 county, and 1 university healthcare system. MAIN OUTCOMES: Main outcomes consisted of self-reported medication underuse as a result of cost, A1C levels, symptom burden, and Medical Outcomes Study 12-Item Short-Form physical and mental functioning scores. RESULTS: Fewer VA patients reported cost-related medication underuse (9%) than patients with private insurance (18%), Medicare (25%), Medicaid (31%), or no health insurance (40%; P <0.0001). Underuse was substantially more common among patients with multiple comorbid chronic illnesses, except those who used VA care. The risk of cost-related underuse for patients with 3+ comorbidities was 2.8 times as high among privately insured patients as VA patients (95% confidence interval, 1.2-6.5), and 4.3 to 8.3 times as high among patients with Medicare, Medicaid, or no insurance. Individuals reporting cost-related medication underuse had A1C levels that were substantially higher than other patients (P <0.0001), more symptoms, and poorer physical and mental functioning (all P <0.05). CONCLUSIONS: Many patients with diabetes use less of their medication than prescribed because of the cost, and those reporting cost-related adherence problems have poorer health. Cost-related adherence problems are especially common among patients with diabetes with comorbid diseases, although the VA's drug coverage may protect patients from this increased risk.
Piette et al. (Mon,) studied this question.