Impact of Medicare part d coverage restrictions on nursing home resident outcomes

In 2006, Medicare Part D transitioned prescription drug coverage for dual-eligible nursing home residents from Medicaid to Medicare and randomly assigned them to Part D prescription drug plans (PDPs). Because PDPs differ in coverage, residents' assigned plans may be relatively more or less generous for drugs they were currently taking. The study objective is to assess the impact of PDP generosity for three medication classes on resident health. Using Medicare claims, Minimum Data Set assessments, pharmacy claims, and PDP formulary information, we use regression models to estimate the impact of PDP coverage restrictions for antidepressants, antipsychotics, and cholinesterase inhibitors on: depression; hallucinations/delusions; aggressive behaviors; cognitive performance; and activities of daily living. We adjust for baseline health status and rely on randomization to PDPs to address the potential selection bias common in observational studies of how plan generosity affects outcomes. In our three medication classes of interest, we find little effect of PDP coverage restrictions on resident health outcomes across a range of specifications. One exception was that antidepressant coverage restrictions had a modestly detrimental effect on residents' mean depression scores – 3.4% on average, relative to residents who faced no restrictions (p<0.05). Our findings suggest that changes in benefit generosity for three commonly-used medication classes had little impact on resident outcomes in 2006-2008. Our results could reflect several factors, including the policy protections in place for dual-eligible nursing home residents and the limited number of residents we observe who face coverage restrictions and subsequently alter medication use in these classes.