|
E-mail this page to a friend!
A Gene Helps Senior Citizens Who Gain Most from
Exercise
Aug. 10, 2005 - Of nearly 3,000 seniors studied,
those who exercised stayed healthier than their couch potato peers, but
those born with a certain gene benefited the most from physical
activity, said Marco Pahor, M.D., director of University of Florida's
Institute on Aging and the senior author of a multi-institutional study.
Genes keep elderly people from benefiting equally from exercise, no
matter how much effort they expend, the study says.
"To our knowledge, this is the first study to show
behavioral and genetic interaction in functioning and aging, and shows
people are already pre-selected, that there are genes that interact with
behavior to affect mobility," Pahor said.
Decreasing mobility, along with lack of muscle
strength and a decline in aerobic ability, are common aspects of aging
that can lead to loss in quality of life, Pahor said. Understanding the
mechanisms of how people lose mobility may lead to ways to help people
remain independent longer, he added.
Federal health statistics have shown that about 34
percent of the U.S. population aged 70 or older reports difficulty
walking a quarter of a mile. These individuals are at much greater risk
of moving into a nursing home or dying over a two-year period, compared
with their counterparts who do not report trouble walking the distance.
And despite the undisputed benefits of exercise,
not everyone responds the same, even when they do lead active lives -
for reasons that have not been entirely clear.
In the current study, researchers assessed senior
citizens in an effort to better understand the relationship between
genetic makeup, intensity of physical activity and functional decline.
Twice a year throughout the four-year study, participants ages 70 to 79
reported their level of activity and their ability to walk a quarter
mile or up 10 stairs.
Researchers also tested the blood of each study
subject to identify which version of a gene long associated with
exercise performance they had. About a third of the population possesses
the DD genotype of the gene, named for the angiotensin-converting
enzyme, or ACE. The rest have the II or ID versions of the ACE gene.
Study participants were categorized according to
their exercise intensity and their genetic makeup. Overall, about 41
percent of study participants became less mobile over the four-year
period. Even though people who exercised were less likely to develop
substantial physical limitations, not everyone received the same
benefits, even if they exercised with the same intensity.
About a third of the seniors engaged in significant
physical exercise including walking and strenuous exercise, and they
preserved their mobility longer than the 70 percent who engaged in
little or no physical activity. Researchers also evaluated the 8 percent
who reported participating in weight training.
But genetic makeup influenced long-term physical
function. Among exercisers, the DD and ID genotypes were more likely to
remain fit than those with the II genotype, who developed mobility
problems at a 45 percent higher rate, researchers found. No difference
in mobility according to genotype was found among non-exercisers,
suggesting function was influenced by an interaction between exercise
intensity and genetic make-up.
In addition, seniors who reported weight training
and had the DD or ID genotype displayed the lowest rate of mobility loss
in any exercise category. In contrast, weight trainers with the II
genotype developed physical limitations similar to those experienced by
seniors who were relatively inactive.
What differences in body composition the genotype
creates also may yield clues to what causes mobility limitations to
develop with age, and what people can do to stay active, Pahor said.
Those with the II genotype, for example, tended to have higher total
body fat.
"The good news is that regardless of genotype, the
physically active people were at lower risk of losing mobility,
suggesting that everyone should exercise to preserve mobility," said
Pahor, a professor and chairman of the College of Medicine's department
of aging and geriatric research.
The study's lead author, Stephen Kritchevsky,
Ph.D., a professor and director of the Sticht Center on Aging at the
Wake Forest University School of Medicine, said that people respond
differently to exercise and that the implications of that response may
change as they age.
"In our study, the II genotype is associated with
increased fat in the leg muscles," Kritchevsky said. "Now energy storage
near muscles may benefit young athletes engaged in endurance activities,
but in older persons, accumulation of leg fat has been linked to poorer
muscle function and metabolic diseases like diabetes."
"This report is one step," he said. "It is
necessary to do more research to determine whether there are other genes
that may affect the benefits of physical activity on functioning of
older adults."
The study, published in today's (Aug. 10) Journal
of the American Medical Association, was funded by the National
Institute on Aging and the Claude D. Pepper Older Americans Independence
Center and conducted in conjunction with researchers at several other
institutions, including the University of Tennessee and the University
of Pittsburgh, opens the door to more research on the interaction of
behavior and genes and how that changes with age, Pahor said.
Click to More Senior News on the
Front Page
Copyright: SeniorJournal.com |
