The effects of health plan copayments on adherence to oral diabetes medication and health resource utilization.

Abstract

To assess the effects of copayments on oral diabetes medication adherence, health resource utilization, and expenditure. Retrospective, observational analysis of medical and pharmacy claims data from PPG Industries employees, retirees, and dependents (2003-2005). Average monthly copayments were stratified low (US$0-9), medium (US$10-19), or high (US$20+). In 2052 individuals, adherence to oral diabetes medication was highest for the low copayment group for both age groups >or=65 years; 84% low, 77% medium, 64% high (P < 0.0001) and <65 years; 74% low, 71% medium, 55% high (P < 0.0001). For patients <65 years, total health care expenditure was 22% lower in the low versus high copayment group (P = 0.024), resulting in average savings of US $3116 per patient per year. Risk of hospitalization was significantly lower in the low versus the high copayment group for patients >or=65 years of age. High copayments were associated with lower adherence to oral diabetes medications for all patients and higher total health care costs for patients less than 65.