Here's more on memory and hormones (cortisol acts through an IR):
Stress May Lead to Mental Decline
By HELEN PHILLIPS
c.1998 Nature News Service
It seems that our hormones, our diets, our lifestyles and our genes all
club together to wear out our bodies and wither away our mental
faculties - a process referred to as aging. When it comes to cognitive
powers, it seems we can now add stress to the list of factors that
speed up our decline.
A report in the first issue of the journal Nature Neuroscience now
finds that continually high levels of stress hormones seem to speed up
aging of the human brain and cause a decline in certain types of
learning and memory.
Alzheimer's disease and normal aging both lead to a decline in a part
of the brain linked to spatial learning and memory. The region, known
as the hippocampus (because it is shaped like a horse's head), is full of
sites where stress hormones could bind, so it seems sensible to
suggest that stress might also affect this part of the brain.
For about 20 years, it has looked as though the hippocampus of
laboratory rats with higher than normal levels of stress hormones aged
more rapidly than normal. But whether the same aging process goes
on in humans has remained hard to test and very controversial.
Now Sonia Lupien of McGill University and The Geriatric Institute of
Montreal, in Quebec, Canada, and her colleagues, have used a
brain-imaging technique, memory tests and a five-year-long study of
levels of the main stress hormone, cortisol, in normal elderly people, to
test the link between stress and brain aging.
They found that the people with the highest cortisol levels, as well as
those with the most rapidly rising levels, had the smallest hippocampal
volumes. Moreover, these people also tended to do less well on the
memory test and at solving mazes (a test of spatial abilities).
Nada Porter and Philip Landfield of the University of Kentucky seem
convinced by the findings. Discussing the work in an accompanying
commentary, they say ''Lupien and colleagues now provide
substantial evidence that long-term exposure to adrenal stress
hormones may promote hippocampal aging in normal elderly humans.''
How does cortisol cause aging? Porter and Landfield make some
suggestions. Stress hormones are designed to divert our energies to
cope with the immediate worries rather than longer-term maintenance.
Cortisol may therefore reduce the levels of the nutrient glucose, slowly
starving the cells. The hormone may also make nerves more likely to
be killed by the body's own clearing-up processes. Additionally, our
mental abilities may be slowed by the remaining cells being less active.
But before we all start worrying about getting stressed, and what it
might do to our brains, Porter and Landfield explain that the problems
are brought about by long-term exposure to stress hormones. Rapid
brain aging is not the result of normal day-to-day worries and stresses.
Long-term individual differences in cortisol levels, however, may
explain why some people's mental abilities decline faster than others as
they grow older. |
