Medicare Advantage in the US mainland and Puerto Rico

To compare enrollment rates in Medicare Advantage (MA) among people with disabilities (PWD) and individuals with end-stage renal disease (ESRD) in the US (50 states and District of Columbia) and Puerto Rico (PR).

This observational study utilized repeated cross-sectional data from the Master Beneficiary Summary File from 2008 to 2022.

The sample included beneficiaries who had continuous Medicare enrollment during the corresponding calendar year and were alive at the end of March 31 the following year. Partial-year MA enrollment was defined as having at least 1 month of MA coverage. Full-year MA enrollment was defined as having continuous MA coverage for all 12 months. We calculated the percentage of enrollees in MA based on their entitlement (age, disability, and ESRD). Standardized differences were calculated to compare characteristics of US and PR enrollees in 2022.

Between 2008 and 2022, our study included 757,245,942 person-years from the US and 10,298,906 person-years from PR. In 2022, Medicare beneficiaries in PR exhibited a higher partial-year MA enrollment rate-nearly double that of the US (84% vs 48%; d  = 0.837; 95% CI, 0.835-0.839). In addition, in the US, the difference between partial-year and full-year MA enrollment rates was 5.7% for PWD and 9.1% for ESRD enrollees. In PR, the differences were 2.7% for PWD and 10.0% for ESRD enrollees.

Discrepancies between partial-year and full-year MA enrollment persisted among PWD and ESRD subpopulations, highlighting potential differences in coverage and access to care for these groups.