Objective: To examine the effects of statin cost-sharing (ie, copayments, coinsurance) on adherence to statin medications and the impact of adherence on healthcare utilization and spending.
Study design: Retrospective, observational study of statin users receiving health benefits or supplemental coverage from employer-sponsored health plans.
Methods: Medical and pharmacy claims were selected from the Medstat MarketScan database for patients who were continuously enrolled from 2000 through 2003. Two-stage residual inclusion models were estimated. The first stage modeled adherence to statins, which was derived from the medication possession ratio, and represented the percentage of days on therapy in an 18-month time frame, July 2001 through December 2002. In the second stage, generalized linear models were used to estimate 2003 utilization and expenditures. Separate estimates were produced for new statin users (n = 24 113) and continuing statin users (n = 93 253).
Results: Lower statin copayments were associated with higher levels of statin adherence. In percentage terms, when holding all other variables at their mean value, a $10 increase in copayment resulted in a 1.8 percentage point reduction in the probability of adherence for new users and a 3 percentage point reduction in the probability of adherence for continuing users. For continuing users adherent to statins, total costs did not change, but fewer negative events (emergency department visits, hospitalizations, and coronary heart disease-related hospitalizations) occurred.
Conclusions: Policy makers and plan managers should consider interventions that improve adherence to statins, such as lower copayments.