How much exercise do we need to live longer?

Gretchen Reynolds

CNA/ THE NEW YORK TIMES – To increase our chances for a long life, we probably should take at least 7,000 steps a day or play sports such as tennis, cycling, swimming, jogging or badminton for more than 2.5 hours per week, according to two large-scale new studies of the relationship between physical activity and longevity.

The two studies, which together followed more than 10,000 men and women for decades, showed that the right types and amounts of physical activity reduce the risk of premature death by as much as 70 per cent.

But they also suggested that there can be an upper limit to the longevity benefits of being active, and pushing beyond that ceiling is unlikely to add years to our life spans and, in extreme cases, might be detrimental.

Plenty of research already suggests that people who are active outlive those who seldom move. A 2018 study by the Centers for Disease Control and Prevention (CDC), for instance, concluded that about 10 per cent of all deaths among Americans aged 40-70 are a result of too little exercise. A 2019 European study found that two decades of inactivity doubled Norwegian people’s risk of dying young.

But scientists have not yet pinned down precisely how much – or little – movement might be most strongly associated with greater longevity. Nor is it clear whether we can overdo exercise, potentially contributing to a shorter life.

The two studies showed that the right types and amounts of physical activity reduce the risk of premature death by as much as 70 per cent. PHOTO: CNA/THE NEW YORK TIMES

Those issues lie at the heart of the two new studies, which look at the links between activity and longevity from distinct but intersecting angles. The first of the studies, published this month in JAMA Network Open, centred on steps.

Most of us are familiar with daily step counts as an activity goal, since our phones, smart watches and other activity trackers typically prompt us to take a certain number of steps every day, often 10,000. But as I have written before, current science does not show that we require 10,000 steps for health or longevity.

Researchers from the University of Massachusetts at Amherst, the CDC and other institutions wondered if, instead, smaller step totals might be related to longer lives. So, they turned to data gathered in recent years for a large, ongoing study of health and heart disease in middle-aged men and women. Most of the participants had joined the study about 10 years earlier, when they were in their 40s. At the time, they completed medical tests and wore an activity tracker to count their steps every day for a week.

Now, the researchers pulled records for 2,110 of the participants and checked their names against death registries. They found that 72 participants had died in the intervening decade, a relatively small number but not surprising given the people’s relative youth.

But the scientists also noticed a strong association with step counts and mortality. Those men and women accumulating at least 7,000 daily steps when they joined the study were about 50 per cent less likely to have died than those who took fewer than 7,000 steps, and the mortality risks continued to drop as people’s step totals rose, reaching as high as 70 per cent less chance of early death among those taking more than 9,000 steps.

But at 10,000 steps, the benefits levelled off.

“There was a point of diminishing returns,” said an assistant professor of kinesiology at the University of Massachusetts Amherst Amanda Paluch, who led the new study.

People taking more than 10,000 steps per day, even plenty more, rarely outlived those taking at least 7,000.

Helpfully, the second study, which was published in August in Mayo Clinic Proceedings, settled on broadly similar activity levels as best bets for long life.

This study involved data from the decades-long Copenhagen City Heart Study, which has recruited tens of thousands of Danish adults since the 70s and asked them how many hours each week they play sports or exercise, including cycling (wildly popular in Copenhagen), tennis, jogging, swimming, handball, weight lifting, badminton, soccer and others.

The researchers focussed on 8,697 of the study’s Danes, who had joined in the 90s, noted their activity habits then and checked their names against death records. In the 25 years or so since most had joined, about half had died. But those who reported exercising, in some way, between 2.6 and 4.5 hours per week when they joined were 40 per cent or so less likely to have died in the interim than less active people.

Translating those hours of exercise into step counts is not an exact science, but the researchers estimate that people exercising for 2.6 hours a week, or about 30 minutes most days, likely would accumulate around 7,000 to 8,000 steps most days, between their exercise and daily life, while those working out for 4.5 hours a week probably would be approaching the 10,000-steps threshold most days.

And at that point, as in the first study, benefits plateaued. But in this study, they then surprisingly declined among the relatively few people who worked out for 10 hours or more per week, or about 90 minutes or so most days.

“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 for 2.6 to 4.5 hours a week, said professor of medicine at the University of Missouri-Kansas City and Director of preventive cardiology at the St Luke’s Mid America Heart Institute Dr James O’Keefe, who was an author on the study.

Both studies are associational, though, meaning they show that physical activity is linked to life span but not that being more active directly causes life spans to lengthen.

Together, however, they provide useful takeaways for all of us hoping to live long and well.

Both studies pinpointed the sweet spot for activity and longevity at somewhere around 7,000 to 8,000 daily steps or about 30-45 minutes of exercise most days. Doing more may marginally improve your odds of a long life, Dr O’Keefe said, but not by much, and doing far more might, at some point, be counterproductive.

Accumulate and measure your activities “in whatever way works for you”, said Dr Paluch.

“Step counting may work well for someone who does not have the time to fit in a longer bout of exercise. 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.”