Health insurance status, cost-related medication underuse, and outcomes among diabetes patients in three systems of care

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 under-use, 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), I county, and I 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 < 0.0061), 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.