Maciejewski ML (Durham HSR&D), Bryson CL
(Seattle HSR&D), Perkins M
(Seattle HSR&D), Sharp N
(Seattle HSR&D), Liu CF
Prior VA and non-VA studies have shown that medication copayments reduce adherence, but few studies have examined which subgroups are most adversely impacted by increased medication copayments. VA increased the copayment for medications from $2 to $7 per 30 days of fill in February 2002. The purpose of this study is to examine whether cost-related medication non-adherence differs between high-risk and low-risk veterans and between veterans on zero or one medication versus taking two or more other medications.
Using a sample of 2,465 veterans with diabetes taking oral hypoglycemic agents (OHAs) and 7,731 veterans with hypertension taking anti-hypertensive medications, we stratified the samples by Diagnostic Cost Group (DCG) risk score (< 1, > 1) and by the number of medications that veterans were taking in the twelve months before baseline (< 2, > 2). We used generalized estimating equations to examine differences in pre- and post-copay changes in adherence to OHAs and anti-hypertensives between veterans exempt from copays and veterans required to pay. We controlled for age, gender, race, marital status, VA site, Census-based per capita income and education attainment in the veteran’s zip code of residence, and time trends.
Among low-risk veterans, veterans required copayments had a greater decline after the copay increase than copay exempt veterans (p=0.006). High-risk veterans in both copay groups had similar adherence between pre and post periods. Veterans taking few (< 2) medications at baseline were similarly adherent regardless of copay status. Among veterans taking two or more medications at baseline, those required copayments had a greater decrease in adherence after the copay increase (p=0.01), compared to copay-exempt veterans.
The 2002 medication copayment increase from $2.00 to $7.00 for a 30-day fill was associated with the greatest cost-related medication non-adherence in veterans with diabetes or hypertension taking multiple medications and those with little comorbidity.
VA policymakers need to evaluate whether the revenue benefits of increased medication copayments are offset by cost-related medication non-adherence by veterans with diabetes or hypertension taking essential medications. VA providers may need to track more closely veterans who report cost-related medication non-adherence to maintain disease control.