April 15, 1998
Web posted at: 10:17 a.m. EDT (1417 GMT)
NEW YORK (AP) -- Chronically
high levels of a stress-related
hormone can shrink a part of the
brain and impair memory in older
people, a study suggests. The
finding might indicate a way to
prevent some age-related memory
loss and even Alzheimer's disease,
researchers say.
The finding does not necessarily mean that a stressful life will
erode
memory, experts said.
The idea that high levels of the hormone cortisol can shrink a
brain
feature called the hippocampus has been suggested before in
studies of people with Alzheimer's or Cushing's syndrome, a
condition that produces high cortisol levels. The new work
indicates it's also true in healthy older people.
Prior studies have also concluded that high cortisol levels can
hamper memory in healthy people.
Scientists haven't yet found out whether elderly people with
chronically high and rising cortisol levels are especially prone
to
getting Alzheimer's or depression, which also robs older people
of
memory. But if they are, medications to cut cortisol levels might
prevent those illnesses, said researcher Sonia Lupien of McGill
University in Montreal.
She and colleagues report the work in the May issue of a new
journal called Nature Neuroscience. Lupien said high cortisol
levels appeared in about a third of 60 volunteers between ages 60
and 85 who've participated in her work, suggesting they might be
fairly common in older people.
The new study included six people who showed high and rising
cortisol levels when monitored annually for 24 hours over five or
six years. The study also had five people with moderate and
decreasing levels. The average age of each group was in the 70s.
Brain scans showed that the hippocampus was 14 percent smaller
on average in the first group than the second. And people in the
first group did worse in remembering a path through a maze and
recalling pictures they'd seen 24 hours earlier, two tasks that
use
the hippocampus.
Cortisol is released by the adrenal gland at times of stress.
Lupien
said she doesn't know why the high-cortisol group in her study
had
chronically elevated levels. It's not known whether their lives
had
been unusually stressful, she said. They do pump out more
cortisol
in response to stressful situations than other people, she said.
Philip Landfield of the University of Kentucky, who was familiar
with the study results, said the finding suggests cortisol and
other
hormones might promote aging of the human brain. That fits in
with
two decades of experiments in animals, he said. The hormones
may also be one reason why elderly people are especially
vulnerable to Alzheimer's, he said.
Landfield also said it would be oversimplifying to conclude that
a
lifetime of stress always makes the brain age faster and lose
powers of memory. That may be true on average, but there can be
many exceptions because individuals probably vary widely in their
response to cortisol and its hormone cousins, he said.
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