Background: Frailty screening using the Clinical Frailty Scale (CFS) has been proposed to guide resource allocation in acute care settings during the pandemic. However, the association between frailty and coronavirus disease 2019 (COVID-19) prognosis remains unclear.

Objectives: To investigate the association between frailty and mortality over 6 months in middle-aged and older patients hospitalized with COVID-19 and the association between acute morbidity severity and mortality across frailty strata.

Design: Observational cohort study.

Setting: Large academic medical center in Brazil.

Participants: A total of 1830 patients aged ≥50 years hospitalized with COVID-19 (March-July 2020).

Measurements: We screened baseline frailty using the CFS (1-9) and classified patients as fit to managing well (1-3), vulnerable (4), mildly (5), moderately (6), or severely frail to terminally ill (7-9). We also computed a frailty index (0-1; frail >0.25), a well-known frailty measure. We used Cox proportional hazards models to estimate the association between frailty and time to death within 30 days and 6 months of admission. We also examined whether frailty identified different mortality risk levels within strata of similar age and acute morbidity as measured by the Sequential Organ Failure Assessment (SOFA) score.

Results: Median age was 66 years, 58% were male, and 27% were frail to some degree. Compared with fit-to-managing-well patients, the adjusted hazard ratios (95% confidence interval [CI]) for 30-day and 6-month mortality were, respectively, 1.4 (1.1-1.7) and 1.4 (1.1-1.7) for vulnerable patients; 1.5 (1.1-1.9) and 1.5 (1.1-1.8) for mild frailty; 1.8 (1.4-2.3) and 1.9 (1.5-2.4) for moderate frailty; and 2.1 (1.6-2.7) and 2.3 (1.8-2.9) for severe frailty to terminally ill. The CFS achieved outstanding accuracy to identify frailty compared with the Frailty Index (area under the curve = 0.94; 95% CI = 0.93-0.95) and predicted different mortality risks within age and acute morbidity groups.

Conclusions: Our results encourage the use of frailty, alongside measures of acute morbidity, to guide clinicians in prognostication and resource allocation in hospitalized patients with COVID-19.