The researchers gathered data, too, about each person’s known risk factors for severe Covid, including their age, smoking habits, weight, and any history of cancer, diabetes, organ transplants, kidney problems and other serious, underlying conditions.
Then the researchers crosschecked numbers, with arresting results. People in the least-active group, who almost never exercised, wound up hospitalized because of Covid at twice the rate of people in the most-active group, and were subsequently about two-and-a-half times more likely to die. Even compared to people in the somewhat-active group, they were hospitalized about 20 percent more often and were about 30 percent more likely to die.
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Of the other common risk factors for severe disease, only advanced age and organ transplants increased the likelihood of hospitalization and mortality from Covid more than being inactive, the scientists found.
“Being sedentary was the greatest risk factor” for severe illness, “unless someone was elderly or an organ recipient,” says Dr. Robert Sallis, a family and sports medicine doctor at the Kaiser Permanente Fontana Medical Center, who led the new study. And while “you can’t do anything about those other risks,” he says, “you can exercise.”
Of course, this study, because it was observational, does not prove that exercise causes severe Covid risks to drop, but only that people who often exercise also are people with low risks of falling gravely ill. The study also did not delve into whether exercise reduces the risk of becoming infected with coronavirus in the first place.
But Dr. Sallis points out that the associations in the study were strong. “I think, based on this data,” he says, “we can tell people that walking briskly for half an hour five times a week should help protect them against severe Covid-19.”
A walk — or five — might be especially beneficial for people awaiting their first vaccine, he adds. “I would never suggest that someone who does regular exercise should consider not getting the vaccine. But until they can get it, I think regular exercise is the most important thing they can do to lessen their risk. And doing regular exercise will likely be protective against any new variants, or the next new virus out there.”