Racial and ethnic disparities in medication adherence among privately insured patients in the United States

To examine the association between socioeconomic status (SES) and racial and ethnic disparities in medication adherence for three widely prescribed therapeutic classes. We linked longitudinal claims data from a large US-based insurance provider (2011-2013) to detailed SES information to identify patients treated with oral antidiabetic (N = 56,720), antihypertensive (N = 156,468) or antihyperlipidemic (N = 144,673) medications. We measured adherence and discontinuation by therapeutic class, and conducted regression analysis to quantify the contributions of different factors in the association between race/ethnicity and medication adherence. During an average follow-up period of 2.5 years, average adherence rates of Blacks and Hispanics were at least 7.5 percentage points lower than those of Whites. Controlling for demographics, health status, out-of-pocket costs, convenience of refilling prescriptions and SES attenuated the association by 30 to 50 percent, nonetheless substantial racial disparities persisted (4.1-5.8 percentage points), particularly for asymptomatic conditions. Separating adherence among existing users from those that discontinued therapies indicates that racial/ethnic disparities in adherence reflect inconsistent pill-taking rather than differential rates of discontinuation. Racial/ethnic disparities in adherence are mitigated, but persist after controlling for detailed socioeconomic measures. Interventions should focus more on improving medication adherence of existing users, particularly in treating asymptomatic conditions.