By Gretchen Reynolds American Journal of Preventive Medicine
Men and women who worked out at least 30 minutes most days were about four times more likely to survive covid-19 than inactive people, according to an eye-opening study of exercise and coronavirus outcomes among almost 200,000 adults in Southern California. The study found that exercise, in almost any amount, reduced people’s risks for a severe coronavirus infection. Even people who worked out for as little as 11 minutes a week — yes, a week — experienced lower risks of hospitalization or death from covid than those who moved about less.
“It turns out exercise is even more powerful than we thought” at protecting people from severe covid, said Robert Sallis, a clinical professor at Kaiser Permanente Bernard J. Tyson School of Medicine in Los Angeles and senior author of the new study.
The findings add to mounting evidence that any amount of exercise helps lower the ferocity of coronavirus infections, a message with particular relevance now, as holiday travel and gatherings ramp up and covid cases continue to rise.
Science already offers copious support for the idea that regular, moderate exercise increases our immune response and generally helps us avoid respiratory infections or recover more rapidly if we do catch a bug. In a 2011 study, adults who worked out regularly were almost half as likely to develop colds or similar infections as inactive people and also about 40 percent less likely to report their illnesses as lingering.
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A similar pattern is emerging in research about covid, with several studies finding that people who are fit and active wind up hospitalized with or dying of covid at much lower rates than people who are out of shape. Sallis led a study last year, for instance, of more than 48,000 patients at the Kaiser Permanente health-care system in Southern California, showing that those who almost never exercised were at much higher risk of severe outcomes from covid, including death, than patients of the same age who were quite active.
But that study, although large in scale, concentrated primarily on two binary groups: those who almost never exercised and those who exercised all the time, passing over the broad swath of people who occasionally work out and leaving important questions unanswered about how much — or, really, how little — physical activity might best help most of us protect ourselves against severe covid.
So, for the new study, which was published this month in the American Journal of Preventive Medicine, Sallis and his colleagues again turned to anonymized records about patients of Kaiser Permanente. Since 2009, that health-care system has included exercise as one of the vital signs health-care workers check during each patient visit, meaning they ask patients how many days per week they exercise, typically by walking, and for how many minutes.
The researchers now drew the records for 194,191 Kaiser patients who had been diagnosed with covid between Jan. 1, 2020, and May 31, 2021, and seen a doctor at least three times in recent years, so their records held multiple mentions of their exercise habits.
Averaging that information, the researchers divided people into five groups, based on how much they moved and whether their habits had changed over the years. The least-active group consisted of those who regularly exercised for fewer than 10 minutes a week. The most active consistently worked out at least 150 minutes per week, which is the amount of exercise recommended by federal health agencies.
In-between were groups whose exercise habits had changed from one medical appointment to the next, but generally kept them moving for more than 10 minutes but fewer than an hour a week, and others who regularly worked out for at least an hour weekly, but fewer than 150 minutes.
The patients, in other words, represented most average people’s exercise routines.
Next, the researchers checked everyone’s medical records for conditions known to contribute to serious covid outcomes, including obesity, high blood pressure and heart disease.
Finally, they cross-checked data about hospitalization or death of covid and people’s exercise habits.
The correlations proved to be “very strong, across-the-board,” Sallis said. The more someone exercised, he said, the less likely he or she was to be hospitalized or die after developing covid.
The differences were most extreme between those who almost never exercised and those who worked out at least 150 minutes per week. The never-exercisers were 391 percent more likely to die after developing covid than the active men and women — whether they had obesity, high blood pressure or existing heart disease.
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But even among those who worked out less often, managing perhaps 10 or 15 minutes a week, that exercise translated into reduced odds of serious covid.
“It is such a simple, inexpensive way to protect yourself,” Sallis said.
The data in the study was collected before widespread coronavirus vaccines were available, but Sallis thinks the results would be similar among vaccinated people.
“The results support the ubiquitous reach of physical activity for health benefits,” said I-Min Lee, a professor of epidemiology at the Harvard T.H. Chan School of Public Health, who studies exercise and health but was not involved with this research.
The study has limitations, though. People self-reported their exercise; it wasn’t objectively tracked. The researchers also looked at improving covid outcomes, not preventing coronavirus infections. And, while they found strong links between being active and avoiding serious covid illness, other factors may be at play. People who exercise might have higher incomes, for instance, or other lifestyle aspects that influence their health, although the researchers tried to account for those issues.
Overall, Sallis said, “the data are just so clear and so strong. To mitigate your risk of severe covid outcomes, get vaccinated and go for a walk.”
