A South Korean study shows a complex relationship between moderate to vigorous physical activity (MVPA) and COVID-19, with a regular exercise habit linked to COVID-19 infection early in the pandemic but also associated with a significantly lower risk of developing severe symptoms. The study was published yesterday in JAMA Network Open.
The study is based on data collected on South Koreans who participated in National Health Insurance Service (NHIS) biennial health screening. Patients were followed from October 8, 2020, until receiving a diagnosis of COVID-19 or December 31, 2021. Results from surveys given to 83,350 patients with COVID-19 (average age, 51.9 years) among 2,110 ,268 participants were identified.
Infection tied to more physical activity
Patients with COVID-19 were compared with controls who avoided infection and asked how and if they engaged in MVPA during two time periods—period 1 (2017-2018) and period 2 (2019-2020).
Disease severity was a secondary outcome, defined as acute clinical events of COVID-19 after hospitalization, including requirement of oxygen supply with conventional oxygen therapy (COT), high-flow nasal cannula (HFNC), continuous positive airway pressure, admission to the intensive care unit (ICU), requirement of mechanical ventilation, and extracorporeal membrane oxygenation (ECMO).
When considering only period 1, the effect size of MVPA did not differ between those who contracted COVID-19 and those who avoided infection. For example, roughly one third of study participants in both groups reported being physically inactive (35.8% vs 35.9% in the COVID-19 and no-COVID-19 groups), while 27.5% of patients with COVID-19 and 27.4% of those without reported MVPA 5 or more times per week.
The authors describe a nonlinear association between COVID-19 infections and MVPA. The authors said unvaccinated patients who engaged in MVPA five or more times per week in period 1 saw their odds for infection decrease when they engaged in MVPA only 1 to 2 times per week (adjusted odds ratio [aOR,] 0.90; 99% confidence interval [CI], 0.81 to 0.98) or were physically inactive (aOR, 0.80; 99% CI, 0.73 to 0.87) during period 2, compared with those who persistently engaged in MVPA 5 or more times per week across both periods.
Less severe disease progression with higher activity
MVPA was associated with less severe disease progression, however.
"Compared with the unvaccinated patients who were persistently physically inactive, the odds for severe COVID-19 clinical outcomes decreased when MVPA increased from physically inactive to MVPA 3 to 4 times per week," the authors said.
Of note, the risk for HFNA, COT, and mechanical ventilation significantly dropped when patients reported MVPA 3 to 4 times per week.
This evidence of an association between MVPA and an increased risk of SARS-CoV-2 infection but a lower the risk of severe COVID-19 outcomes is striking and can be controversial compared with previous studies
"This evidence of an association between MVPA and an increased risk of SARS-CoV-2 infection but a lower the risk of severe COVID-19 outcomes is striking and can be controversial compared with previous studies," the authors wrote.
The authors said the inhalation of respiratory droplets and proximity to others may define the link between MVPA and COVID-19 infection before vaccines were widely available.
Both being vaccinated and engaging in MVPA was associated with less disease severity, the authors said, and the relationship is circular. "Being vaccinated not only protects from the disease but also encourages regular MVPA by the sense of security against COVID-19, which has numerous health benefits," they wrote.
