Health

Even ‘light’ physical activity is linked to a lower risk of early death

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The health benefits from physical activity for middle-aged and older adults may be twice as large as previously reported, according to a large study published Thursday in The BMJ (formerly known as the British Medical Journal).

Any kind of physical activity seems to confer those benefits — even “light” activities, such as cooking a meal, weeding a flowerbed or walking the dog, the study also found. The important thing is to get up and move — and to do it regularly and often.

That also means not sitting for prolonged periods. A high amount of sedentary time — seven hours or more per day (not including time spent sleeping) — was linked in the study to an increased risk of early death.

“Since sedentary behaviors and physical activity seem to be interrelated, a simple public health message would be to ‘sit less — move more and more often,’” write two of the study’s authors  — Ulf Ekelund, a sports medicine professor at the Norwegian School for Sport Sciences in Oslo, and Thomas Yates, a physical activity researcher at the University of Leicester — in a commentary about the research on the BMJ’s website.

Current U.S. physical activity guidelines recommend a minimum of 150 minutes per week of moderate-intensity exercise for optimal health. The guidelines also state that prolonged sitting should be avoided, but they do not specify how much is too much.

That how-much-is-too-much question is widely debated, Ekelund and Yates point out. Also unclear (and debated) is whether levels of physical activity below those in the guidelines are still beneficial — and whether light-intensity physical activity counts at all. The primary reason for those uncertainties is that physical activity guidelines are based on studies in which people self-reported how much and how intensely they exercised. Such reports are susceptible to error.

How the study was done

To address those issues, Ekelund, Yates and their colleagues, conducted a systematic review and meta-analysis of eight previous studies that had used portable accelerometers — not self-reports — to measure their participants’ physical activity. The studies involved 36,383 people aged 40 and older (average age: 62) from four countries (Norway, Sweden, the United Kingdom and the United States). The health — and deaths — of the participants were followed from four to 14.5 years (average: 5.8 years).

The authors of the meta-analysis pooled the accelerometer data from those eight studies and then re-examined it. They looked at the intensity (light, moderate or vigorous) and duration (low or high) of the participants’ physical activity, as well as at their sedentary time.  The participants were then divided into four groups, from lowest to highest, for each of those categories.

During the studies’ follow-up periods, 2,149 (almost 6 percent) of the participants died. The researchers then compared the chances of death for the participants in the different activity groups.

What the study found

After adjusting for various other factors that can increase the risk of early death, such as age, smoking, body mass index (a measure of obesity) and socioeconomic status, the researchers found that almost any amount of physical activity — even light activity — was linked to a significantly lower likelihood of early death. Benefits were greatest, however, for people who did:

  • 24 minutes a day (168 minutes per week) of moderate- to vigorous-intensity physical activity, such as brisk walking, biking or recreational swimming
  • 375 minutes (6 hours 25 minutes) a day of light-intensity physical activity, such as cooking, gardening or walking slowly

“The observation that light intensity physical activity also provided substantial health benefits is important for public health,” write Ekelund and Yates, “as this suggests that older people and those who are not able to be physically active at higher intensities will still benefit from just moving around.”

As the researchers point out, the associations between physical activity and the risk of death were much stronger than those found in previous studies that relied on people’s self-reports of their physical activity.

“The risk of dying was approximately 60% lower in the most active quarter [of the participants] compared with the least active quarter,” Ekelund and Yates point out. “If we express this in absolute numbers per 1,000 participants, 23 individuals died in the most active 25% of the participants compared with 130 deaths per 1,000 participants in the least active 25% — more than a five-fold difference between groups.”

The meta-analysis also found a strong association between high amounts of sedentary time and early death. People in the studies who spent the most time sitting were 263 percent — more than twice as likely — to have died than those who spent the least time sitting. The risk began to climb when daily sitting time reached 7 to 9 hours, but the big increase came after 9.5 hours.

Limitations and implications

This is an observational study, so it doesn’t prove a causal connection between physical activity and the risk of early death. In addition, the results are applicable only to older people and those who live in high-income countries.

Still, this is the largest study to date to look at the links between objective physical activity data (collected by accelerometers) and the risk of early death

As an editorial that accompanies the meta-analysis points out, getting people to change unhealthy habits and be more physically active — the “holy grail of primary care and public health” — is challenging, particularly at the population level. Indeed, research has shown that American adults have not increased their physical activity levels at all over the past decade, although they are spending more time sitting.

Walking offers, perhaps, the most promising way of getting people to be more active. “It is simple, affordable (free), achievable even for older adults, and rarely contraindicated,” the authors of the editorial points out.

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