Physical Activity Levels and Lung-Kidney Function in a Cohort of COVID-19 Survivors

Background: The relationship between physical activity levels and overall health among survivors of moderate to severe COVID-19 remains underexplored in target organs, such as lungs and kidneys. We examined the association between physical activity levels and lung-kidney abnormalities in survivors of COVID-19 hospitalization. Methods: A cross-sectional analysis was performed within a prospective cohort of survivors of COVID-19 hospitalization. Physical activity levels were assessed with the International Physical Activity Questionnaire (short form), and physical inactivity was classified according to the WHO guidelines (<150 min/week of physical activity). Abnormal kidney function was defined as estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m 2 , whereas pulmonary involvement was defined as chest X-ray pulmonary lesion, and/or forced vital capacity < the lower limit of normal, and/or altered oximetry. Results: 653 survivors (46% female and 28% ≥65 years) were assessed 8±2 months post-hospital discharge. Physical inactivity was found in 53% of the cohort. Lung and kidney abnormalities were observed in 36% and 20% of survivors, respectively, whereas coexistence in 7%. Physically active survivors had lower odds of lung abnormality (32% vs . 41%; adjusted odds ratio [aOR]=0.67, 95%CI:0.47 to 0.97), but not of kidney (17% vs . 23%; aOR=0.81, 95%CI:0.52 to 1.26) nor lung-kidney abnormality (6% vs . 9%; aOR=0.58, 95%CI:0.29 to 1.20), compared to those physically inactive. Subgroup and sensitivity analyses showed distinct associations for lung abnormalities by age and among survivors without severe oxygen desaturation or very low kidney function. The restricted cubic spline curve for lung-kidney abnormalities showed a non-linear dose-response relationship, with higher odds below and lower odds above 150 min/week. Conclusions: Among survivors of COVID-19 hospitalization, being physically active was associated with better lung function outcomes, but not kidney or composite outcomes. This association was modified by age and baseline clinical status and followed a non-linear dose-response pattern.