San Francisco -- Middle-aged people with excess visceral fat --
usually apparent in the thick waist or pot belly of an apple-shaped
body -- are nearly three times more likely to suffer from dementia
in their 70s and 80s than people with little to no belly fat,
according to a study of Kaiser Permanente patients.
Researchers have long connected obesity, diabetes and heart
disease to dementia. The new study -- published Wednesday in
Neurology, the journal of the American Academy of Neurology --
suggests that the effect of fat on the body is more complicated
than just a number on a scale.
"People need to think not just about weight, but where they
carry their weight," said Rachel Whitmer, a research scientist at
Kaiser's Division of Research in Oakland and lead author of the
study. "They need to know if they're apples or pears."
People with pear-shaped bodies tend to carry most of their
weight below the waist, in the hips, buttocks and thighs. People
with apple-shaped bodies are at greater risk of having too much
visceral fat surrounding internal organs deep in the abdominal
cavity. Visceral fat is more common in people who are overweight,
but even a very lean person with a small pot belly could have
hidden visceral fat.
Researchers don't yet understand why visceral fat is
particularly dangerous, but the fat is metabolically active and
doctors think it may release toxins associated with atherosclerosis
or plaque build-up in the brain that is apparent in people with
Alzheimer's disease, Whitmer said.
In the Kaiser study, researchers looked at records from patients
in their 40s and 50s who had their abdominal fat measured in the
1960s and '70s. Of the 6,583 patients studied, 15.9 percent had
been diagnosed with dementia by 2006.
Among patients with the most visceral fat in middle age, the
rate of dementia was 324.3 cases per 10,000; patients with the
least belly fat had a rate of dementia of 214.6 cases per 10,000.
When the data was adjusted for factors that can affect dementia
- including age, education, sex, and medical conditions such as
stroke or heart disease -- people with the most belly fat were 2.72
times more likely to develop dementia than those with the least
fat.
Even thin people could be at risk if they have a large pot
belly. In the study, patients who were of average weight but in the
category with the most visceral fat were 89 percent more likely to
develop dementia than people of average weight with little or no
belly fat.
c.2008 SAN FRANCISCO CHRONICLE