BACKGROUND: Cardiac rehabilitation (CR) can improve cardiovascular health. We identified whether CR participation was associated with fewer subsequent inpatient hospitalizations and emergency department visits and less Medicare and out-of-pocket expenditures, and whether outcomes varied by amount of participation. METHODS: This retrospective study used Medicare fee-for-service claims data, including beneficiaries with a CR-qualifying event in 2016. Participants attended ≥2 sessions of CR within 365 days of the event. Propensity score matching was used to identify CR-eligible nonparticipants. Difference-in-differences analyses were used to compare differences in outcomes before (2014-2015) and after (2018-2019
2-year CR period=2016-2017) the CR period between participants and nonparticipants. RESULTS: We identified 57 668 CR-eligible beneficiaries after matching, with equal numbers of participants and nonparticipants. Nearly 65% of beneficiaries had a percutaneous coronary intervention, 33.5% had an acute myocardial infarction, 17.5% had a coronary artery bypass graft, and 16.8% had a heart valve repair/replacement. Compared with nonparticipants, participants had 47.6 fewer subsequent annual inpatient hospitalizations per 1000 beneficiaries (95% CI, -58.8 to -36.3) and 005 lower subsequent annual Medicare expenditures per beneficiary (95% CI, -352 to -59). Compared with no participation, medium participation (12-23 sessions), high participation (24-35 sessions), and CR completion (≥36 sessions) were associated with fewer inpatient hospitalizations and lower Medicare expenditures per year. CONCLUSIONS: CR was associated with fewer subsequent annual inpatient hospitalizations and lower subsequent annual Medicare expenditures. A higher amount of participation was associated with a further reduction in hospitalizations and expenditures. These findings can inform programs and policies that encourage CR participation.