The researchers also collected data on each person's known risk factors for severe Covid, including their age, smoking habits, weight, and a history of cancer, diabetes, organ transplants, kidney problems, and other serious underlying diseases.
Then the researchers checked the numbers with startling results. People in the least active group who almost never played sport were hospitalized twice as often for Covid as people in the most active group and then died about two and a half times more often. Even compared to people in the somewhat active group, they were hospitalized about 20 percent more often and about 30 percent more likely to die.
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Of the other common risk factors for serious illness, only advanced age and organ transplants increased the likelihood of hospitalization and mortality from Covid more than inactive, the scientists found.
"Sedentary lifestyle was the biggest risk factor" for serious illness, "unless someone was older or an organ recipient," says Dr. Robert Sallis, a family and sports medicine specialist at Kaiser Permanente Fontana Medical Center, who led the new study. And while "there is nothing you can do about these other risks," he says, "you can exercise."
Of course, since this is an observational study, this study does not prove that exercise reduces serious Covid risks, but only that people who do frequent sport are also people with a low risk of getting seriously ill. The study also did not look at whether physical activity actually reduced the risk of coronavirus infection.
Dr. However, Sallis points out that the associations in the study were strong. "I think based on this data," he says, "we can tell people that brisk walking five times a week for half an hour should help protect them from severe Covid-19."
A walk – or five – might be especially beneficial for people waiting for their first vaccine, he adds. “I would never suggest that someone who exercises regularly should consider not getting the vaccine. But until you get it, I think regular exercise is the most important thing you can do to reduce your risk. Exercising regularly will likely protect against new variants or the next new virus. "