OBJECTIVES : Enrollment in Medicare Advantage (MA) has grown significantly over the past two decades, with one of three Medicare beneficiaries now covered by an MA plan. Yet we know little about their characteristics or experiences due to lack of access to data for beneficiaries enrolled in these private health plans. This study used a unique source of data from more than 150 MA plans nationwide to analyze MA enrollees’ demographic, socioeconomic, and clinical characteristics as well as their health care utilization, spending, and quality of care.

METHODS : Retrospective observational cohort analyses of Medicare encounter data for more than 2 million MA beneficiaries in 2012 and 1.8 million in 2015. Beneficiaries were required to be continuously enrolled with medical and pharmacy benefit coverage for each 12-month reporting year.

RESULTS : Between 2012 and 2015, the MA population grew younger and included greater proportions of racial and ethnic minorities. There were also more low-income beneficiaries, more living in high poverty neighborhoods, and more living in neighborhoods where few residents have college degrees. While chronic conditions had not become more prevalent by 2015, a greater proportion of beneficiaries had more complex medical needs. Hospitalization rates were stable but lengths of hospital stays increased as did use of observation stays and emergency department visits. Spending was 13 percent higher in 2015, largely due to spending on prescription drugs especially among the highest cost beneficiaries (79% higher). Performance on several measures of health care quality improved, but medication adherence declined slightly.

CONCLUSIONS : MA plans will need to develop targeted interventions to address beneficiaries’ social risks, avoid medical complications that result in emergency room use and preventable hospital stays, and increase medication adherence. Plans also need to reduce spending on postacute care, for example by expanding use of services provided in beneficiaries’ homes.