Linked to Memory Loss
NEW YORK (Reuters Health) -
Middle-aged and older adults with a condition that often precedes
diabetes appear to show signs of memory loss not visible in their
peers without the condition, researchers announced Monday.
In addition, people with insulin
resistance--a loss of sensitivity to this key blood-sugar-regulating
hormone--tended to have a relatively small hippocampus, a region
in the brain associated with short-term memory.
"This (finding) might give baby
boomers a motivation to get off their couches and on their treadmills,"
said Dr. Antonio Convit of New York University and the Nathan
Kline Institute for Psychiatric Research in Orangeburg, New York.
Although insulin resistance commonly
results from excess weight and lack of exercise, most people who
have the condition don't know it, and may consider themselves
to be perfectly healthy, Convit told Reuters Health.
So while people may not be motivated
to exercise and diet to improve their appearance, Convit said
he hoped that the thought that their lifestyle was affecting their
memories, as well as the shape of their brains, might do the trick.
Past studies have suggested that full-fledged diabetes can also
put people at risk of memory problems.
In the new study, Convit and his
team obtained their findings from brain scans, memory tests, and
tests of insulin resistance in 30 people without diabetes who
were between 53 and 89 years old. They reported their results
in the early online edition of the Proceedings of the National
Academy of Sciences.
In an interview, the researcher
explained that when people become resistant to insulin--a condition
also known as impaired glucose tolerance--they have trouble getting
glucose (blood sugar) out of the blood and into the tissues that
During the test of glucose tolerance,
Convit and his colleagues injected people with a certain amount
of glucose--roughly equivalent to two donuts' worth, Convit said--and
took many blood samples.
The authors discovered that people
who had more trouble clearing glucose from their blood also tended
to perform less well during tests of short-term memory. Brain
scans also revealed that the size of the hippocampus tended to
be smaller in people with insulin resistance.
Convit explained that the brain
relies on glucose for fuel, and the hippocampus is especially
vulnerable to stress. People with insulin resistance are unable
to bring glucose to where it needs to go, he said, and a lack
of fuel might affect how well the brain--in particular, the hippocampus--develops.
Whether these memory problems are
permanent or not remains unclear, he said. However, diabetics
who get their condition under control often also see an improvement
in their memory, Convit noted, a sign that reduced memory is also
reversible in pre-diabetics.
For people who know or fear they
are insulin resistant and "want to retain as much of their marbles
as possible," Convit recommended that they exercise and lose any
excess weight--the best methods of getting blood sugar under control,
SOURCE: Proceedings of the National
Academy of Sciences 2003;10.1073/pnas.0336073100.
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