Prescription coverage, use and spending before and after Part D implementation: a national longitudinal panel study.

Background: In January 2006, 43 million Medicare beneficiaries became eligible for subsidized prescription coverage (Part D) through Medicare. To date, no longitudinal study has afforded information on beneficiaries' prescription coverage transitions and corresponding changes in prescription use and spending.
Objective: To evaluate changes in Medicare beneficiaries' prescription coverage, use and spending before and after Part D implementation, including comparison of those who enrolled in Part D with those who did not.
Design, Setting and Participants: Longitudinal observational study of non-institutionalized Medicare beneficiaries aged 65 and older (n = 9,573) employing administrative data from the Centers for Medicare and Medicaid Services (CMS) and survey-based data from beneficiaries (2003, 2006). Sampling drew from a 1% national probability sample (2003), oversampling low-income beneficiaries including those dually-enrolled in Medicare and Medicaid. MEASUREMENTS & MAIN RESULTS: Number and type of prescriptions, monthly out-of-pocket prescription spending, and cost-related non-adherence to prescription regimens. Most respondents who lacked prescription coverage in 2003 had acquired it by 2006 (82.6%)-primarily through Part D (63.1%). Part D enrollees who previously lacked coverage or had Medigap coverage appear particularly advantaged by Part D, as evidenced by significantly increased prescription use, lower out-of-pocket spending and lower non-adherence. Those with employer-based coverage experienced significantly increased spending. Among those still lacking coverage in 2006, high rates of cost-related non-adherence (31.8%) were reported by the low-income, chronically ill subgroup.
Conclusions: In its first year, Part D coverage appears to have moderated prescription spending and cost-related burden for those who previously had meager benefits or none. Increased spending among those with employer-based coverage may reflect a narrowing of those benefits over this period. Evidence of foregone care among low-income, chronically ill seniors who still lack prescription coverage highlights the importance of targeted outreach to this group for Part D's low-income subsidy program.