Older people who exercise three or more
times a week are less likely to develop Alzheimer's and
other types of dementia, according to a study that adds
to the evidence that staying active can help keep the
mind sharp.
Researchers found that healthy
people who reported exercising regularly had a 30 to 40
percent lower risk of dementia.
The study, published Tuesday in the Annals of Internal
Medicine, reached no conclusions about whether certain
types of exercise helped more than others, but researchers
said even light activity, such as walking, seemed to help.
"It seems like we are delaying onset," said Dr. Wayne
McCormick, a University of Washington geriatrician who
was one of the study's authors. "The surprising finding
for us was that it actually didn't take much to have this
effect."
Some researchers have theorized that exercise might reduce
brain levels of amyloid, a sticky protein that clogs the
brain in Alzheimer's patients.
The study, from 1994 to 2003, followed 1,740 people ages
65 and older who showed no signs of dementia at the outset.
The participants' health was evaluated every two years
for six years.
Out of the original pool, 1,185 people were later found
to be free of dementia, 77 percent of whom reported exercising
three or more times a week; 158 people showed signs of
dementia, only 67 percent of whom said they exercised
that much. The rest either died or withdrew from the study.
The study could not say if exercise helped prevented
dementia altogether, because not all of the participants
were followed up to their deaths.
The frequency of dementia was 13 per 1,000 person years
for those who said they exercised three or more times
a week, compared with 19.7 per 1,000 person years for
those who reported exercising less.
Other researchers said randomized studies — in which
participants would be randomly assigned to either exercise
or maintain their usual habits — are needed to confirm
the findings.
Bill Thies, vice president for medical and scientific
affairs for the Alzheimer's Association, said a randomized
trial with more people could help answer questions such
as what types of exercise might help more than others.
"You would have to start with a group that had roughly
common habits, and change those habits in one group and
not in the other," Thies said.
