Cardiorespiratory fitness and physical activity and risk of SARS-CoV-2 and COVID-19 hospitalization: the HUNT study

BACKGROUND: Physical activity (PA) has been associated with a reduced risk of severe COVID-19 outcomes. However, the relationship between cardiorespiratory fitness (CRF) and the risk of SARS-CoV-2 infection and COVID-19 hospitalization has not been thoroughly investigated. We aimed to investigate the association of estimated CRF (eCRF) and leisure-time PA (LTPA) with risk of SARS-CoV-2 infection and COVID-19 related hospitalization in a general population of Norwegian adults. METHODS: (mL/kg/min) and LTPA was categorized based on metabolic equivalent hours per week (MET h/wk): inactive (0-3.5 MET h/wk), insufficiently active (> 3.5 to 7.5 MET h/wk), and sufficiently active (> 7.5 MET h/wk). Poisson regression was used to estimate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for the association of eCRF and LTPA with SARS-CoV-2 infection and COVID-19 hospitalization. RESULTS: Age averaged 53.6 years (SD 16.8) and 53.9% were women. During 2.6 years of follow-up there were 5991 SARS-CoV-2 infections and 218 COVID-19 related hospitalizations. Fitness and LTPA categories did not associate with risk of infection. However, adults with the highest eCRF had significantly lower risk of hospitalization compared to adults with the lowest eCRF (IRR, 0.54, 95% CI, 0.34-0.86). Similarly, sufficiently active adults (> 7.5 MET h/wk) prior to the pandemic had significantly lower risk of being hospitalized compared to inactive adults (IRR, 0.60, 95% CI, 0.47-0.83). CONCLUSIONS: Higher eCRF and LTPA were not associated with risk of SARS-CoV-2 infection. In contrast, adults with high eCRF and LTPA were associated with a lower risk of COVID-19 related hospitalization compared to adults with low fitness and inactive lifestyles.