April 16, 2015

To Live Longer, What Amount and Type of Exercise is Best?

Two just-released studies underscore the importance of exercise. Published last week in JAMA Internal Medicine, they define how much exercise might be enough, quantify the risks of getting too little, and suggest there’s no real harm in getting “too much” vigorous exercise.

How Much Exercise is Best?
The first study -- Leisure Time Physical Activity and Mortality: A Detailed Pooled Analysis of the Dose-Response Relationship -- assembled data about people’s exercise habits from six large health studies still in progress. Researchers from Harvard, the National Cancer Institute, and several other institutions placed over 661,000 adults – mostly middle aged – into categories based on the amount of time they spent exercising each week.

Those subgroups ranged from people who didn’t exercise at all to people who exercised moderately for 25 or more hours every week. Somewhere in between were those people who actually followed the 2008 Physical Activity Guidelines for Americans: a minimum of 75 minutes vigorous-intensity or 150 minutes of moderate-intensity exercise each week.

After stratifying all those people into their appropriate exercise categories, the researchers examined the death records for all groups. Here’s what they found:
  • Hardly a surprise: people who did not exercise carried the highest risk of early death.
  • People who exercised just a little – even well short of the recommended 150 minutes per week – reduced their risk of early death by 20%.
  • People who hit that recommended guideline exactly were 31% less likely to die early than those who didn’t exercise.
  • People who tripled the recommended guideline (3 x 150) – logging about 450 minutes of moderate exercise each week – showed the best results of all, reducing their risk of early death by 39%.
  • The super-exercisers – people who went at it for 25 or more hours each week – experienced early death rates similar to those who simply met the 150-minutes-each-week guideline. “More” wasn’t necessarily “better,” but “more” didn’t hurt, either… contrary to much of the conventional wisdom out there.

What Kind of Exercise is Best?

In this study, Australian researchers reviewed the health data of more than 200,000 adults, quantifying each participant’s exercise time, and then qualifying it, too. Did they walk or run? Did they play competitive singles tennis or leisurely social doubles?  

Then, the researchers evaluated death statistics among all groups, and drew these conclusions:
  • People who met the exercise guideline reduced their early death risk significantly, even if the exercise was only moderate, like walking.
  • People who spent up to 30% of their weekly exercise regimen in “vigorous” activities showed a premature death risk that was 9% lower than those who exercised for the same amount of time, but always “moderately.”
  • People who spent more than 30% of their regimens in “strenuous” activities had an early death risk that was 13% lower than those “merely moderate” exercisers.
  • People who exercised “intensely” showed no increased early death risk.

While the researchers evaluated reliable death statistics, the results from both studies include participants’ fallible recollections. Therefore, these conclusions can only reveal associations  – not cause and effect -- between amounts and types of exercise on the one hand, and early death risks on the other.

Still, those associations seemed meaningful enough for the study authors to confidently make these recommendations:
Leisure Time Physical Activity and Mortality (first study above):
Meeting the 2008 Physical Activity Guidelines for Americans minimum by either moderate- or vigorous-intensity activities was associated with nearly the maximum longevity benefit. We observed a benefit threshold at approximately 3 to 5 times the recommended leisure time physical activity minimum and no excess risk at 10 or more times the minimum. In regard to mortality, health care professionals should encourage inactive adults to perform leisure time physical activity and do not need to discourage adults who already participate in high-activity levels. 
Effect of Moderate to Vigorous Physical Activity on All-Cause Mortality in Middle-aged and Older Australians (second study):
Among people reporting any activity, there was an inverse dose-response relationship between proportion of vigorous activity and mortality. Our findings suggest that vigorous activities should be endorsed in clinical and public health activity guidelines to maximize the population benefits of physical activity.

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