卫生类B级：阅读理解High Stress May
According to a report issued in May 1998， elderly people who consistently
high blood levels of the stress hormone. Whats more ，high levels of cortisol
are also associated with shrinking of the hippocampus(海马区)， a region of the
brain that plays a key role in learning and memory.
The findings suggest that even cortisol levels in the normal， "healthy"
range can actually accelerate brain aging.
The study results "now provide substantial evidence that long-term exposure
to adrenal(肾上腺) stress hormones may promote hippocampal aging in normal elderly
humans， "write Nada porter and Phillip Landfield. Cortisol is a hormone releases
in response to stress by the adrenal glands(腺)， which sit on top of the kidneys(肾).
Over a 5-to 6-year period， dr. Sonia lupine and his colleagues measures
24-hour cortisol levels in 51 healthy volunteers， most whom were in their 70s.
The researchers tested the volunteers memory on six people in the
increasing/high category and five people in the decreasing/moderate group. The
groups did not differ in tests of immediate memory， but the increasing/high
cortisol group had other memory problems compared with those in the
decreasing/moderate group.
The researchers also found that the total volume of the hippocampus in
those in the increasing/high group was 14% lower than those in the
decreasing/moderate group， although there were no differences in other brain regions.
The results suggest that "…brain aging can be accelerated by levels of
adrenal hormones that are not generally regarded as pathological(病态的) and that
variation within this normal range is related to variation in the rate of brain
aging." write porter and landfield." This further suggests that chronic stress
may accelerate the worsening of the hippocampus.