Abstract 14924: Gender Differences in Cardiac Rehabilitation Participation and Outcomes in a National Medicare Sample: An Instrumental Variable Approach

Background: Cardiac rehabilitation (CR) participation following percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) decreases patient morbidity and mortality. Many studies are underpowered to evaluate gender differences. We aimed to look at gender differences in CR use and short term outcomes including 1-year mortality in a national Medicare sample. Methods: We identified Medicare beneficiaries over 65 years undergoing PCI and CABG from 07/2016-12/2018. Primary exposures included female vs. male sex and CR use within one year of discharge based on outpatient claims. Clinical outcomes included 1-year mortality and readmissions. We analyzed differences in characteristics, CR use, and associated outcomes between females and males using multivariable and instrumental variable analyses using distance to CR facility as the instrument. Results: 414,730 beneficiaries underwent PCI and CABG, of which 145,512 (35.1%) were female. Females were more likely to be older, Black race, dual eligible, live in distressed communities, and have a CR facility in their zip code, and were less likely to be Hispanic, elective procedures, or undergo CABG. CR use was lower for females than males (32.2% vs. 40.5%, p<0.001), which remained significant after adjustment for patient covariates (OR=0.91, 95% CI: 0.89-0.92, p<0.001). One-year mortality for CR users vs. non-CR users was 2.1% / 2.4% and 15.4% / 14.5% for women and men, respectively. One-year readmissions for CR users and non users was 34.3% / 31.2% and 52.8% / 45.0% for women and men, respectively. The adjusted and IV-adjusted average absolute effect of CR use on mortality was similar for females and males but was stronger on 1-year readmissions for females vs. males (Figure). Conclusion: Female Medicare beneficiaries attend CR following PCI and CABG at lower rates than men, but have increased benefit with CR participation on 1-year readmissions with similar mortality benefit relative to men.