Association of cardiorespiratory fitness measured by cardiopulmonary exercise testing with covid-19 positivity: a prospective register-based cohort study

Background It has been suggested that high cardiorespiratory fitness (CRF) may reduce the risk of infection and severe health outcomes for COVID-19. However, there is a need of studies to examine the association between objectively measured CRF and risk of COVID-19 infection. Purpose The objective of this study was to investigate if CRF measured by cardiopulmonary exercise testing is associated with risk of COVID-19 infection. Methods In this prospective register-based cohort study, we linked collected data from the Trøndelag Health Study (HUNT) (n = 2,408, 48,3% women) in Norway with the Norwegian Surveillance System for Communicable diseases (MSIS) registry. Included participants were tested for CRF as peak oxygen uptake (VO2peak) during cardiopulmonary exercise testing between 2017-2019. The individual data were matched with MSIS indicative of having COVID-19 by reporting a positive PCR-test between 26th of February 2020 and 1st of October 2022. Participants were classified into age- and sex-specific quintiles, and modified Poisson regression with log link was used to estimate adjusted relative risk (aRR) and 95% confidence intervals (CI) for the association of CRF with testing positive for COVID-19. Results During a median follow up of 2.6 years, 249 participants tested positive for COVID-19. After adjustment for confounders, participants in the highest quintile of CRF had a significantly lower risk (aRR = 0.59, 95% CI: 0.40 to 0.88) of testing positive for COVID-19, compared with those in the lowest quintile of CRF. Each MET higher CRF was associated with lower risk of COVID-19 infection (aRR = 0.92, 95% CI: 0.87 to 0.98). Conclusions This is the first study to assess the association between objectively measured CRF and risk of COVID-19 infection in a general population of healthy adults. The findings suggest a protective effect of high CRF on COVID-19 infection and highlight the importance of improving CRF to lower the burden of COVID-19 in the general population.