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.