Association of Copayment and Statin Adherence Stratified by Socioeconomic Status

Abstract

There is a growing body of evidence supporting means testing out of copayment for high-value therapies such as statins. To investigate association between statin adherence and copayment when stratified by socioeconomic status. This was a retrospective cohort study set in a network of VA facilities that includes Southern California and Nevada, with an enrollment of 1.4 million veterans. Socioeconomic status was estimated using zip code median household income. Differences in medication possession ratio (MPR) associated with copayment was the primary outcome measure. Odds of attaining low-density lipoprotein cholesterol (LDL) <100 mg/dL was the secondary outcome measure. Separate regression models for each income quintile were performed for each outcome measure, respectively. A total of 4748 patients were included in the analysis. Patients in quintiles two (-0.057, 95% confidence interval [CI] = -0.095 to -0.020) and three (-0.044, CI = -0.081 to -0.007) had statistically significant decreases in MPR associated with having a copayment versus not having a copayment. Quintiles two (odds ratio [OR] = 0.68; 95% CI = 0.47 to 0.98) and three (OR = 0.66; 95% CI = 0.45 to 0.96) also had lower odds of attaining LDL <100 mg/dL when having a copayment. Patients in higher earning quintiles (four and five) did not show any associations with copayment. In the veteran population studied, the association of statin copayment status with adherence varied by socioeconomic status. Middle-income and lower-middle-income patients were more likely to have adherence negatively influenced by having a copayment for statin therapy.