Rebecca A. G. Christensen, Jasleen Arneja, Kate St. Cyr, Shelby L. Sturrock, Jennifer D. Brooks
Abstract
It has been suggested that cardiorespiratory fitness (CRF) may be used to identify those at greatest risk for severe COVID-19 illness. However, no study to date has examined the association between CRF and COVID-19. The objectives of this study were to determine whether CRF is independently associated with testing positive with or dying from COVID-19.
Introduction
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel virus that was first detected in December 2019 [1] and has rapidly evolved into a global pandemic. As of September 9, 2020, there were 27,628,190 reported cases of coronavirus-disease 19 (COVID-19) worldwide, with 898,757 reported deaths [2].
Cardiorespiratory fitness (CRF) is the ability of the body to supply oxygen to skeletal muscles during sustained activity and increases with regular physical activity [11]. CRF is an objective, reproducible measure that captures the health benefits of sustained physical activity [12]. CRF is also an established predictor of cardiovascular disease [13–15] and all-cause mortality [13–15], independent of age and body mass index—risk factors associated with COVID-19 severity and mortality. In fact, CRF has been found to better predict heart disease than assessments of physical activity, suggesting that it may be the better assessment of being active [16]. As such, several groups have hypothesized that high CRF may reduce the risk, severity, and duration of viral infections, including COVID-19 [17, 18]. However, to date, no study has examined the association between CRF and COVID-19 infection or mortality.
Methods
This prospective cohort study has been conducted using the UK Biobank (UKB) Resource [19]. Research Ethics approval was received from the University of Toronto Research Ethics Board (REB) (protocol #39368). Individual participants provided written consent for their data to be shared with external researchers who have REB approval to access the UKB. Therefore, the specific research team for this project did not collect any consents. The UKB is a large population-based cohort that recruited approximately 500,000 adults aged 40 to 69 years from 2006 to 2010. In 2009, the UKB added a baseline CRF assessment, which 95,152 participants (18.9%) completed.
At baseline, questionnaires were used to capture demographic information (e.g., education, ethnicity) and medical history, while trained technicians measured height, weight, and conducted physical health assessments (e.g., CRF). Details of the recruitment process and data collection can be found elsewhere [19, 20].
Discussion
This is the first study to examine the relationship between eCRF and COVID-19 infection and mortality. While we found that eCRF was not associated with risk of testing positive for COVID-19, we found evidence of a dose-response relationship wherein people with higher eCRF have a lower risk of dying from COVID-19.
Patients with severe COVID-19 may experience significant decreases in lung function, potentially requiring mechanical ventilation [33], and respiratory and circulatory failure are common causes of death among COVID-19 patients [34]. Since CRF measures the ability of these systems to supply oxygen to skeletal muscles during sustained activity, CRF may help identify individuals at the greatest risk for severe COVID-19 outcomes [17]. Consistent with this hypothesis, we found that low CRF more than doubled individuals’ risk of dying from COVID-19. In addition, having moderate to high CRF significantly decreased the risk of COVID-19 mortality, with high CRF reducing the risk of mortality even more than moderate CRF, suggestive of dose-response.
Citation: Christensen RAG, Arneja J, St. Cyr K, Sturrock SL, Brooks JD (2021) The association of estimated cardiorespiratory fitness with COVID-19 incidence and mortality: A cohort study. PLoS ONE 16(5): e0250508. https://doi.org/10.1371/journal.pone.0250508.
Editor: Robert Siegel, Cincinnati Children’s, UNITED STATES
Received: September 29, 2020; Accepted: April 7, 2021; Published: May 5, 2021.
Copyright: © 2021 Christensen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: Data cannot be shared publicly because this is third party data which also contains identifiable information. Data are available from the UK Biobank for researchers who meet the criteria for access to the data. Researchers interested in accessing the data can contact access@ukbiobank.ac.uk.
Funding: The authors received no specific funding for this work.
Competing interests: The authors have declared no competing interests exist.
