Two new studies suggest that a "sweet spot" of 7,000 to 8,000 steps—or around 30 to 45 minutes of exercise—a day is key to living a longer life, Gretchen Reynolds reports for the New York Times.

What two new studies reveal about exercise and longevity

According to Reynolds, past research has indicated that people who are physically active tend to live longer than those who are not.

For instance, a 2018 CDC study found that around 10% of all deaths among Americans ages 40 to 70 were the result of insufficient exercise. And a 2019 study presented at the European Society of Cardiology's annual meeting found that Norwegians who were inactive for 20 years doubled their risk of dying at a young age.

And in two new studies, scientists may have determined precisely how much exercise is most strongly associated with greater longevity and whether too much exercise can potentially lead to negative health effects, Reynolds reports.

In the first study, which was published JAMA Network Open, researchers analyzed the association between the number of steps people took each day and their longevity.

Although 10,000 steps are often used as a daily activity goal, the researchers wanted to see if smaller numbers of steps could also be related to increased longevity, Reynolds reports.

For the study, the researchers pulled data from a large, ongoing study of health and heart disease among middle-aged men and women. Participants had originally joined the study around a decade earlier when they were in their 40s. When they joined, the participants completed medical tests and wore an activity tracker that counted their steps every day for a week.

The researchers analyzed the data of 2,110 participants and checked their names against death registries. In total, 72 participants had passed away in the decade after they joined the study.

Although relatively few of the participants had passed away, the researchers noticed a strong association between step counts and mortality. Specifically, men and women who took at least 7,000 steps a day were 50% less likely to have died than those who took fewer than 7,000 steps a day. In addition, they found that people's mortality risk continued to drop as their step totals increased, with a 70% less chance of early death among those who took more than 9,000 steps a day.

However, at 10,000 steps, the health benefits plateaued. The researchers found that people who walked more than 10,000 steps a day rarely lived longer than those who walked at least 7,000.

"There was a point of diminishing returns," said Amanda Paluch, an assistant professor of kinesiology at the University of Massachusetts Amherst and leader of the study.

A second study published in Mayo Clinic Proceedings examined largely similar activity levels and how they affected mortality.

In this study, researchers used data from the Copenhagen City Heart Study, which has recruited tens of thousands of adults in Denmark since the 1970s and asked them how many hours a week they play sports or exercise.

The researchers analyzed the information of 8,697 Danish participants who had joined the original study in the 1990s and checked their names against death records. In the 25 years since most of them had joined, around half had passed away.

However, the researchers found that participants who had reported exercising between 2.6 and 4.5 hours a week were 40% less likely to have died than those who were less active.

Although the hours of exercise could not be translated to exact step counts, the researchers estimated that people who exercised for 2.6 hours a week, or around 30 minutes a day, would likely take around 7,000 to 8,000 steps a day between exercising and daily activities, while people who exercised 4.5 hours a week would likely reach 10,000 steps most days.

Similar to the results of the first study, the researchers in this study found that health benefits leveled off at around 10,000 steps. In addition, the researchers found the few people exercising 10 or more hours a week, or around 90 minutes a day, experienced less health benefits than those who exercised less often.

"The very active group, people doing 10-plus hours of activity a week, lost about a third of the mortality benefits" compared to people exercising between 2.6 and 4.5 hours a week, James O’Keefe, a professor of medicine at the University of Missouri-Kansas City and one of the study's authors, said.

Key takeaways

According to Reynolds, both studies are associational, meaning that while they show physical activity is linked to life span, they do not indicate that being more active can directly increase longevity.

In general, what both studies suggest is that the "sweet spot" for activity and longevity is around 7,000 and 8,000 steps a day, or about 30 to 45 minutes of exercise a day.

While exercising more than that may slightly improve your chances of living a long life, it won't be by much, O'Keefe said. He added that doing far more exercise may also become counterproductive at some point.

And if you want to increase your own activity levels, Paluch recommends getting exercise "in whatever way works for you."

"Step counting may work well for someone who does not have the time to fit in a longer bout of exercise," Paluch said. "But if a single bout of exercise fits best with your lifestyle and motivations, that is great as well. The idea is just to move more." (Reynolds, New York Times, 9/15)