This is the first study to demonstrate that Medicare Part D was associated with increased use of heart failure medications. These findings are consistent with a major goal of the policy which was to reduce financial barriers to medication access among the elderly. Previous studies have shown that, before Part D, rates of prescribing of and adherence to pharmacotherapy regimens for heart failure were suboptimal.19, 20
For example, only 43.6% of incident heart failure patients in the Cardiovascular Health Study were taking a beta blocker.20
We report a significant increase in beta blocker use among those without coverage in 2004-05 who obtained Part D benefits, from 45% to 59%. Evidence linking beta blocker use with reduced 1-year mortality rates in older adults21
suggests that this increased use may reduce mortality among Medicare beneficiaries with heart failure.
Our study also showed that medication refill adherence for heart failure improved with Part D. A previous study by Madden et al24
using national data from the Medicare Current Beneficiary Survey showed that Part D reduced the rate of self-reported cost-related non-adherence from 15% to 11%, however, the analysis did not stratify by level of drug coverage or clinical condition. We found that the proportion of older adults with heart failure who lacked drug coverage prior to Part D who had good adherence with an ACEI or ARB and beta blocker increased from 67% in 2004-2005 to 78% in 2006-2007. Given the impact of improved medication adherence in older adults with heart failure on health care use and costs7
this improvement could lead to reductions in health care costs overall for this population. We note that adherence in the comparison group fell significantly over the study period. This finding is consistent with evidence of poor long-term adherence to medications used to treat or prevent cardiovascular disease.25
In spite of the reduction in adherence during the study period, adherence rates in the No Cap group tended to be higher for this group compared to those in Part D. This is likely due to the gap in coverage or “donut hole” for those with Part D benefits and its impact on adherence.26
It is important to note that expansions in drug coverage did not appear to increase the use of second line agents (e.g., digoxin or aldosterone-inhibiting diuretics) for heart failure in older adults. This may reflect prescribers’ awareness of the high rate of serious adverse drug reactions with these medications when used in older adults with heart failure.22, 23
It is also possible that we were underpowered to detect statistically significant changes in the use of these agents.
There are some potential limitations to our study. Using ICD-9 codes to identify heart failure may result in some misclassification, although restricting the sample to those filling prescriptions for medications indicated for heart failure has high specificity.27
We could not identify those with diastolic heart failure for whom ACE/ARB plus beta blockers may not be indicated. We do not, however, expect misclassification to differ across pharmacy benefit groups; thus our estimates of Part D’s effect should be unaffected. Some persons without drug benefits may have filled prescriptions at non-network pharmacies before Part D which may result in overestimation of the policy’s effect. However, patients had a strong financial incentive to present their insurance card at network pharmacies; they pay 15% less even when no payment is made by the insurer. We also limited our analyses to those filling at least one prescription in a network pharmacy to minimize censoring. Prescription fills may overestimate actual medication use. However, prescription fills provide similar estimates of adherence to self-report and Medication Event Monitor Systems (MEMS®).28
Lastly, this study of community-dwelling elders living in Pennsylvania enrolled with a single insurer may not be nationally representative. However, our study population spans the range of pharmacy benefits in existence at Part D’s implementation.
In summary, Medicare Part D was associated with improved access to medications and adherence to pharmacotherapy in older adults with heart failure. Future studies should examine the impact of Medicare Part D on the quality of prescribing and related health outcomes.