Natural history of COVID-19: Risk factors for hospitalizations and deaths among >26 million U.S. Medicare beneficiaries

Izurieta, Hector S; Graham, David J; Jiao, Yixin; Hu, Mao; Lu, Yun; Wu, Yue; Chillarige, Yoganand; Wernecke, Michael; Menis, Mikhail; Pratt, Douglas; Kelman, Jeffrey; Forshee, Richard

BACKGROUND: Evaluate risk factors for severe COVID-19 outcomes among Medicare beneficiaries during the pandemic’s early phase. METHODS: Retrospective cohort study covering Medicare fee-for-service (FFS) beneficiaries. We separated out elderly residents in nursing homes (NH) and those with end-stage renal disease (ESRD) from the primary study population of individuals ages ≥65. Outcomes included COVID-19 hospital encounters and COVID-19-associated deaths. We estimated adjusted odds ratios (ORs) using logistic regression. RESULTS: We analyzed 25,333,329 elderly non-NH non-ESRD beneficiaries, 653,966 elderly NH residents, and 292,302 ESRD patients. COVID-related death rates (per 10,000) were much higher among elderly NH residents (275.7) and ESRD patients (60.8) than the primary study population (5.0). Regression-adjusted clinical predictors of death among the primary population included immunocompromised status (OR: 1.43), frailty index conditions such as cognitive impairment (3.16) as well as other comorbidities including congestive heart failure (1.30). Demographics-related risk factors included male sex (1.77), older age (OR: 3.09 for 80-year-old vs. 65-year-old), Medicaid dual-eligibility status (2.17) and racial/ethnic minority. Compared to Whites, ORs were higher for Blacks (2.47), Hispanics (3.11), and Native Americans (5.82). Results for COVID-19 hospital encounters were consistent. CONCLUSIONS: Frailty, comorbidities, and race/ethnicity were strong risk factors of COVID-19 hospitalization and death among the U.S. elderly.