A small study, published Monday in the Proceedings of the
National Academy of Sciences (news
- web
sites), showed that middle-aged and elderly people with high
blood sugar actually had a smaller hippocampus, the brain region so
crucial for recent memory.
The good news: If the findings are confirmed, simple diet and
exercise could help many people protect their brains. Maybe the
threat of memory loss will provide the final push for aging baby
boomers to take those steps, said lead researcher Dr. Antonio Convit
of New York University.
"That's a great motivator to stay off the calories and stay off
the couch," he said.
For every Alzheimer's patient, there are eight older people who
suffer enough memory loss to significantly harm their quality of
life even though they have no dementia-causing disease, said Convit,
an NYU psychiatry professor who set out to uncover the causes.
Blood sugar was a natural suspect because scientists have long
known that diabetics (news
- web
sites) are at higher-than-normal risk for memory problems.
Diabetes harms blood vessels that supply the brain, heart and other
organs.
The new study found that people's memory may be harmed long
before they ever develop full-fledged diabetes and that it's a
problem of fuel, not plumbing.
Convit studied 30 non-diabetic middle-aged and elderly people. He
measured how they performed on several memory tests; how quickly
they metabolized blood sugar after a meal; and, using MRI scans, the
size of the hippocampus.
The slower those outwardly healthy people metabolized blood
sugar, the worse their memory was and the smaller their
hippocampus was, Convit found.
Unlike most other tissues that have multiple fuel sources, the
brain depends on blood sugar for almost all its energy, Convit
explained. The longer that glucose stays in the bloodstream instead
of being metabolized into body tissues, the less fuel the brain has
to store memories.
Convit's research found no specific threshold at which memory
automatically worsened. Overall, though, the slower the glucose
metabolism, the worse people did.
Once that metabolism reaches certain levels, it becomes a
condition called "impaired glucose tolerance" or pre-diabetes,
thought to afflict 16 million Americans. It strikes mostly in middle
age, although people of any age who are overweight and sedentary are
at risk. Without treatment, pre-diabetes usually turns into
full-fledged diabetes, which in turn brings deadly heart attacks,
kidney failure and numerous other ailments.
Why did only the memory-crucial hippocampus seem harmed? Previous
animal and human research shows it's the region most likely damaged
by any brain insult, Convit said. Conversely, it's also a very
adjustable region, with the potential for some recovery if people
bring their blood sugar under control, he said.
Convit's study sheds important light on yet another risk of bad
blood sugar, said Dr. Fran Kaufman, president of the American
Diabetes Association.
She cautioned that it was a small study that requires
confirmation before doctors test glucose solely for memory
complaints.
But if confirmed, the same advice for lowering people's overall
diabetes risk drop a few pounds and do exercise as simple as
walking 30 minutes a day apparently would help protect people's
brains, too, Kaufman said.
Meanwhile, the diabetes association already recommends
pre-diabetes testing for everyone 45 or older, and for younger
people who are significantly overweight and have one other risk
factor: a diabetic relative; bad cholesterol; high blood pressure;
diabetes during pregnancy; birth to a baby bigger than 9 pounds; or
belonging to a racial minority.
