Impact of Cardiorespiratory Fitness on COVID-19-Related Outcomes: The Exercise Testing and Health Outcomes Study (ETHOS)

Abstract

Objective: To assess the association between cardiorespiratory fitness (CRF) and COVID-19-related health outcomes including mortality, hospitalization, and mechanical ventilation.

Patients and methods: In a retrospective analysis of 750,302 patients included in the Exercise Testing and Health Outcomes Study, we identified 23,140 who had a positive result on COVID-19 testing between March 2020 and September 2021 and underwent a maximal exercise test in the Veterans Affairs Health Care System between October 1, 1999 to September 3, 2020. The association between CRF and risk for severe COVID-19 outcomes, including mortality, hospitalization due to COVID-19, and need for intubation was assessed after adjustment for 15 covariates. Patients were stratified into 5 age-specific CRF categories (Least-Fit, Low-Fit, Moderate-Fit, Fit, and High-Fit), based on peak metabolic equivalents achieved.

Results: During a median of follow-up of 100 days, 1643 of the 23,140 patients (7.1%) died, 4995 (21.6%) were hospitalized, and 927 (4.0%) required intubation for COVID-19-related reasons. When compared with the Least-Fit patients (referent), the Low-Fit, Moderate-Fit, Fit, and High-Fit patients had hazard ratios for mortality of 0.82 (95% CI, 0.72 to 0.93), 0.73 (95% CI, 0.63 to 0.86), 0.61 (95% CI, 0.53 to 0.72), and 0.54 (95% CI, 0.45 to 0.65), respectively. Patients who were more fit also had substantially lower need for hospital admissions and intubation. Similar patterns were observed for elderly patients and subgroups with comorbidities including hypertension, diabetes, cardiovascular disease, and chronic kidney disease; for each of these conditions, those in the High-Fit category had mortality rates that were roughly half those in the Low-Fit category.

Conclusion: Among patients positive for COVID-19, higher CRF had a favorable impact on survival, need for hospitalization, and need for intubation regardless of age, body mass index, or the presence of comorbidities.