Exercise and CVD: Timing Isn't Everything

JoAnn E. Manson, MD, DrPH


August 22, 2023

This transcript has been edited for clarity.

This is Dr JoAnn Manson, professor of medicine at Harvard Medical School and Brigham and Women's Hospital. I'd like to talk with you about a recent report in JAMA on exercise and cardiovascular disease (CVD), trying to disentangle the role of the total amount or volume of moderate to vigorous physical activity weekly vs the frequency or pattern of activity. The latter means whether the activity is equally distributed across the week or tends to occur on only 1-2 days, such as a "weekend warrior" pattern.

This was a very large study done in the UK Biobank, including 90,000 men and women with a mean age of 62 years. An objective measure of physical activity was done through accelerometers for 1 week, and then they looked at the incidence CVD events over about 6 years They classified the participants as either meeting the guidelines for moderate to vigorous physical activity of at least 2.5 hours per week, or being physically inactive. They further subdivided the physically active group into those who had an equal distribution of their activity throughout the week vs those whose activity was concentrated into 1-2 days of the week.

They found that both of the active groups, whether they had fairly equal distribution of activity across the week or tended to concentrate their activity into 1-2 days during the week, had similar reductions in CVD. The CVD reductions were quite substantial for myocardial infarction; close to 30% reduction for heart failure, a 35%-40% lower risk for atrial fibrillation, and about a 20% reduction in stroke. The numbers were very similar in the two active groups compared with the inactive groups.

They also did a separate analysis using a threshold for moderate to vigorous activity of 4 hours per week instead of 2.5 hours per week, with very similar results. Another important finding was that the women in the study tended to be much less active than the men. The percentages of women who were classified as inactive or not meeting activity guidelines was about 40% compared with 26% of the men.

The message that being active only 1-2 days of the week (and not necessarily spread out evenly across the week) is very helpful. It's important for cardiovascular health and should be highlighted with women in particular, because women often have greater challenges finding the time to exercise regularly throughout the week.

We know that exercise is as close to a magic bullet as we've found in modern medicine, and this study focused on CVD. But other studies have documented that physical activity is linked to lower risk for type 2 diabetes, osteoporosis, several forms of cancer, and even cognitive decline. So this is a very important message for patients — that exercising has major benefits, even if it can't be done every day of the week, as long as they are meeting the guidelines for total amount of moderate to vigorous physical activity. It seems to be fine if it's concentrated in only 1-2 days of the week. This message can provide more flexibility for patients in achieving physical activity goals and can really help our patients to improve their health.

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