Extra Pounds at Midlife May Boost Dementia Risk
MONDAY, May 2 (HealthDay News) -- Being overweight during middle
age may increase your risk of developing dementia later on, a new
Swedish study suggests.
Several studies have already linked obesity in middle age to
dementia in later life, but it was unclear whether merely carrying
some extra pounds in midlife was a risk factor. The new research
suggests that even being overweight -- defined as having a body
mass index (BMI) of 25 to 30 -- is linked with a higher risk of
"Being overweight at midlife increased the risk of dementia in late life by more than 70 percent," said lead study author Dr. Weili Xu, a postdoctoral researcher at Karolinska Institute in Stockholm.
Being obese raised the risk even more, to nearly fourfold.
"Although the effect of midlife overweight on dementia is not as substantial as that of obesity, its impact on public health is significant," Xu said, noting that 1.6 billion adults worldwide are obese or overweight, including 50 percent of adults in the United States and Europe.
The study is published in the May 3 issue of
In her study, Xu analyzed information from the Swedish Twin
Registry. It included data on 8,534 twins aged 65 and older. Of
those, 350 were diagnosed with dementia and 114 with possible
Thirty years earlier, the participants had provided what then
must have seemed like mundane data: their height and weight.
That data would prove invaluable as Xu grouped them according to
their BMIs, from underweight to obese (having a BMI higher than
30). Nearly 30 percent, she found, were either overweight or obese
Further analysis showed that being overweight or obese in
midlife independently increased the risk of later dementia,
including Alzheimer's and vascular dementia.
About 26 percent of participants without dementia had been
overweight at midlife, compared to 36 percent of those with
possible dementia and 39 percent with diagnosed dementia.
And although 2.7 percent of seniors without dementia had been
obese at midlife, 6.9 percent of those with dementia had been
obese, as well as 5.3 percent of those with possible dementia.
When Xu analyzed twin pairs in which one had dementia in later
life and one did not, she found the link to weight no longer
significant, suggesting early environment and genetics also play
roles in dementia.
Why the weight-dementia link? Several mechanisms could explain
it, Xu said. A higher BMI is linked with diabetes and vascular
disease, which is in turn related to the risk of dementia. Higher
weight at midlife may reflect a long period of exposure to higher
inflammation throughout the body, which has been linked with lower
Xu and her colleagues noted several study limitations, including
the notion that BMI may not be the perfect measure of body fat
They also noted that in terms of lowering dementia risk, it's
never too late to start reducing body fat.
The study has a number of strengths, including the large number
of people studied, according to Dr. Gary Kennedy, director of
geriatric psychiatry at Montefiore Medical Center and professor of
psychiatry and behavioral science at Albert Einstein College of
Medicine in the Bronx.
Although the study finds a link between being overweight in
midlife and dementia risk, it does not prove cause-and-effect, he
said. Still, there is evidence that fatty tissue secretes
inflammatory cytokines and other chemicals. These may have a direct
effect on the brain, he said, inflicting damage to the neurons.
Dr. Gisele Wolf-Klein, director of geriatric education at the
North Shore-Long Island Jewish Health System in Hyde Park, N.Y.,
said the study "is of great relevance in view of the growing
epidemic of obesity in both the United States and Europe."
To learn more about body mass index, visit the
National Heart, Lung, and Blood Institute.
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