The Impact of Prescription Drug Coverage on Disparities in Adherence and Medication Use: A Systematic Review.

Prescription drug cost-sharing is a barrier to medication adherence, particularly for low-income and minority populations. In this systematic review, we examined the impact of prescription drug cost-sharing and policies to reduce cost-sharing on racial/ethnic and income disparities in medication utilization. We screened 2,145 titles and abstracts and identified 19 peer-reviewed papers that examined the interaction between cost-sharing and racial/ethnic and income disparities in medication adherence or utilization. We found weak but inconsistent evidence that lower cost-sharing is associated with reduced disparities in adherence and utilization, but studies consistently found that significant disparities remained even after adjusting for differences in cost-sharing across individuals. Study designs varied in their ability to measure the causal effect of policy or cost-sharing changes on disparities, and a wide range of policies were examined across studies. Further research is needed to identify the types of policies that are best suited to reduce disparities in medication adherence.