The study findings are a bit tricky to understand since they examine only the possible effects of physical activity at one point in a person's life, not throughout their lives.
For example, the study found that white women who were physically active at age 20 were expected to live three years longer than others. But that's based only on reports of how active they were at age 20 -- it's not clear whether they had to remain active over the rest of their lives to get those extra years.
As for older people, the study estimates that white men and women get a lifespan boost of 1.2 and 1.6 years, respectively, if they're active at age 80.
Hispanics appeared to gain nothing in terms of life span from physical activity, although that could be because the surveys weren't properly designed to ask questions appropriate to their culture, Janssen said.
The findings also are limited because it's possible that something other than activity -- such as a healthful diet -- boosted life spans in those who lived longer. The researchers did try to account for that, however.
Dr. Mark Wahlqvist, a visiting professor at Taiwan's National Health Research Institutes who studies physical activity, said a wider Taiwanese study released last year showed that as little as 15 minutes of activity a day can make a difference in terms of longer life span.
But will those extra years be good ones? Wahlqvist thinks so. "It is very likely that they will be ones with better social, mental and physical health," he said.
For more about exercise, try the U.S. National Library of Medicine.
SOURCES: Ian Janssen, Ph.D., associate professor, department of community health & epidemiology, Queen's University, Kingston, Ontario, Canada; Mark Wahlqvist, M.D., former chairman, internal medicine, Monash Universit
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