By now, it’s undeniable: regular exercise comes with a range of health benefits for people who stick with it over time. But is it ever too late to start?

Most research hasn’t been designed to answer this question, since exercise studies typically record people’s physical activity levels at one point in time: in youth, middle-age or beyond. But Pedro Saint-Maurice, a postdoctoral fellow at the National Cancer Institute of the National Institutes of Health (NIH), and his colleagues wanted to find out whether exercise’s benefits changed if people remained active for most of their lives, or if, like most of us, they waxed and waned in sticking to their exercise regimen over their lifetimes.

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“We don’t know much about long-term participation in exercise,” he says. “How does keeping an active lifestyle, or going down and up again, or remaining at low levels of activity impact health risks?”

In a study published in JAMA Network Open, they asked more than 315,000 U.S. adults — between ages 50 and 71 — about their leisure-time activity at four different points in their lives: when they were 15-18 years, 19-29 years, 35-39 years and 40-61 years.

People who said they exercised anywhere from two to eight hours a week at each time period had a 29% to 36% lower risk of dying from any cause during the study’s 20-year period, compared to people who rarely or never exercised. They also lowered their risk of dying from heart disease by up to 42% and cancer by up to 14% compared to inactive people. The more people exercised, the greater their risk reductions.

Given the many health benefits of exercise, that’s not shocking. But Saint-Maurice was surprised when he looked at people who were not active when they were younger, but who increased their exercise levels after their 40s beyond levels they had when they were younger. They also showed declines in their risk of dying early that were similar to those of people who exercised consistently throughout their lives — a drop of 32% to 35% compared to people who didn’t exercise. Drops in heart disease and cancer risk were similar to the steady exercisers, too. For these people as well, those who increased their exercise levels the most saw the greatest benefits.

So why bother exercising consistently throughout your lifetime? There are other benefits, both mental and physical, to staying consistently active — plus, experts say, if you make a habit of exercising when you’re young, you’re more likely to keep up those patterns later in life. The more important message, says Saint-Maurice, is that the results suggest it may not matter as much when you start a exercise regimen. Even if it’s later, you’ll still benefit.

“It’s good to maintain an active lifestyle at all times regardless of your age,” says Saint-Maurice. “But one good thing is that if you have not been active, you can still benefit if you start becoming active in your 40s and 50s, based on our results.”

It’s worth noting that the people were reporting on their exercise habits from decades ago, so there might have been recall errors. And the survey did not ask which types of exercise people were doing. Most of the people who were exercising were getting the government-recommended 150 minutes of moderate-to-vigorous physical activity per week. Research shows that physical activity doesn’t have to occur in big chunks; even small amounts can add up.

Other studies have hinted at why exercise may be so effective at lowering the risk of early death. Regular physical activity can reduce obesity, as well as Type 2 diabetes, which are both risk factors for heart disease and can contribute to premature aging and death.

“It’s a great message,” says Saint-Maurice, “to know that it’s not too late if you haven’t been on the right exercise trajectory.”

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