Researchers compared mortality rates with activity levels among 661,137 men and women over 14.2 years in an effort to gauge the dose-response relationship between leisure time physical activity (LTPA) and mortality generally, with a focus on finding out if an “upper limit” of activity exists in which the longevity benefits level off—or actually decrease.
Some of what they found is already widely accepted: namely, that adhering to the 2008 Physical Activity Guidelines for Americans of 75 vigorous-intensity or 150 moderate-intensity activity minutes a week significantly reduces mortality. Other findings were new, particularly when it came to how much activity produces the biggest longevity payoff. Results were published in the April 6, 2015, online version of JAMA Internal Medicine (abstract only available for free).
By using self-reported activity data from 6 large-scale studies and then converting those data to metabolic equivalent of task (MET) numbers, researchers were able to compare results even when the studies asked slightly different questions about physical activity. The study sample consisted of 291,485 men and 369,652 women, although with a rate of 95% Caucasian participants it was not representative of the US population.
The analysis found that individuals who met or engaged in twice the guideline recommendations (7.5 to 14.9 METs per week) lowered their risk of mortality by 31%, and those who exceeded recommendations by 2 to 3 times (15 METs to 22.4 METs per week) saw a 37% drop. However, that benefit tapered off and finally plateaued at 3 to 5 times the minimum. From that point on, no additional activity—even activity that exceeded the guidelines by 10 times or more—seemed to make a dent in longevity rates.
Authors described the additional benefit of increased activity as “modest,” writing that “meeting the recommended guidelines by either moderate- or vigorous-intensity physical activities was associated with nearly the maximum longevity benefit.” Another study from Australia, published the same day in the same journal, looked more closely at the effects of vigorous vs moderate activity and found a positive relationship between increasing proportions of vigorous activity and further declines in mortality rates.
While spending large amounts of time engaging in physical activity didn’t necessarily translate to a commensurate increase in longevity, researchers also found no support for the opposite hypothesis—that there’s an upper limit to physical activity, beyond which increased activity actually negatively impacts mortality. “Thus, current trends in increasing marathon or triathlon participation should not cause alarm, at least with regard to mortality,” authors write.
In an invited commentary accompanying the article, author Todd M. Manini, PhD, points to the study results as more evidence that primary care providers need to engage patients in conversations that encourage simply following the minimum requirements, where the most significant longevity benefits occur.
Unfortunately, according to Manini, those conversations aren’t happening enough.
“The fact that only approximately one-third of adults received counseling [in physical activity] from a physician or other health professional is disappointing, although this rate has improved by 40% from 2000 to 2010,” Manini writes.
APTA is a strong and vocal advocate for the ability of physical activity to transform society through its effects on public health. The association offers a prevention and wellness webpage with resources on how physical therapists and physical therapist assistants can help individuals become more physically active. Additionally, the association’s MoveForwardPT.com website stresses the importance of physical activity in ways designed to be easily understood by the general public. The association is also on the board of the National Physical Activity Plan alliance, a high-profile effort to create a comprehensive set of policies, programs, and initiatives to increase physical activity in all segments of the American population.
The study’s authors write that their findings do a kind of double duty.
“These findings are informative for individuals at both ends of the physical activity spectrum,” they write. “They provide important evidence to inactive individuals by showing that modest amounts of activity provide benefit for postponing mortality while reassuring very active individuals of no exercise-associated increase in mortality risk.”
Research-related stories featured in PT in Motion News are intended to highlight a topic of interest only and do not constitute an endorsement by APTA. For synthesized research and evidence-based practice information, visit the association’s PTNow website.
American Physical Therapy Association