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More muscle power means lower Alzheimer's risk
Reuters
NEW YORK (Reuters Health) � Older people with stronger muscles are at
reduced risk of developing Alzheimer's disease compared to their
weaker peers, a new study shows.
Dr. Patricia A. Boyle of Rush Alzheimer's Disease Center in Chicago
and her colleagues found that the greater a person's muscle strength,
the lower their likelihood of being diagnosed with Alzheimer's over a
four-year period. The same was true for the loss of mental function
that often precedes full-blown Alzheimer's.
Studies have linked grip strength to Alzheimer's, while a person's
weight and level of physical activity also influence risk of the
disease. To date, however, no one has studied whether muscle strength
in and of itself might play a role in dementia risk, Boyle and her
team note in November's Annals of Neurology.
"These findings support the link between physical health and cognition
in aging and the importance of maintaining good physical function and
strength," Boyle told Reuters Health via E-mail.
The researchers measured the strength of nine muscle groups in the
arms and legs of 970 dementia-free men and women 54 to 100 years old
(their average age was around 80). They also tested the strength of
study participants' breathing muscles.
During follow-up, which lasted about four years, 138 people developed
Alzheimer's. These individuals were older and had worse mental
function than the rest of the study participants. They also were
weaker.
But even after the researchers adjusted for age and education
level-which can influence Alzheimer's risk-they found that muscle
strength had a strong influence on the risk of the disease. People who
ranked in the top 10 percent for muscle strength were 61 percent less
likely to develop Alzheimer's than the weakest 10 percent. Stronger
people also showed a slower decline in their mental abilities over
time.
The relationship between muscle strength and mild mental difficulties,
which occurred in an additional 275 people, was similar, with the
strongest 10 percent being at 48 percent lower risk than the weakest
10 percent.
When the researchers looked at different types of muscle strength
separately, they found that grip strength and breathing-muscle
strength had an independent effect on Alzheimer's risk, but arm and
leg strength didn't.
The most likely explanation for the mental function-muscle strength
link is that there is something going in the body that causes both
muscle weakness and loss of mental ability, Boyle said.
While the study couldn't show whether keeping one's muscles strong
will keep Alzheimer's at bay, staying fit is a good idea-and good for
the brain-no matter what, according to Boyle.
"We certainly think that it is important to be physically active and
to work to keep our muscles strong," she said. "Good physical health
is important for good brain function."
SOURCE: Archives of Neurology, November 2009.