www.sciencenews.org/aaas2010
Longer sleep can boost older brains
study finds uninterrupted rest matters more for the young
By Laura Sanders
Quantity, not quality, of sleep may determine how well older people’s brains function the next day, researchers reported
February 21. For youngsters, though,
quality may be more important. Sleep
affects young and old brains differently,
the study shows, and the findings may
ultimately lead to new ways to offset age-related cognitive decline.
The link between sleep and learning
has been well-established, comments
Matthew Walker of the University of
California, Berkeley. “It’s critical to sleep
before learning. Sleep almost prepares
the brain like a dry sponge to soak up
new information.”
Contrary to common belief, older
adults don’t sleep substantially less
than younger adults. From age 35 to 85,
people actually lose only about an hour
of nightly sleep on average, psychologist
and study coauthor Sean Drummond of
the University of California, San Diego
said. Rather, what changes is sleep
Sleep quality seemed to have no effect
on performance, Drummond said. “For
older adults, the absolute minutes of
sleep they got last night has a significant
influence on performance today.”
In younger folks, on the other hand, the
quality of sleep was critical, Drummond
found. Young adults who slept with lim-
ited interruption performed better and
had higher brain activity in
certain regions than those
who woke up frequently dur-
ing the night.
efficiency — a measure of the portion
of time spent tossing, turning or lying
awake in bed. “The biggest, most common, most robust change is that we
spend more time awake in the middle of
the night,” Drummond said.
In the new study, 33 adults
with a mean age of 67 and
29 adults with a mean age
of 27 slept in a lab while
Drummond and colleagues
measured the duration and
quality of their sleep. The
next day, the researchers
tested participants’ brain
activity and performance on
a learning and memory task.
Older adults who had slept for more
total time the previous night were able
to more accurately remember a list of
random nouns than older adults who
had slept fewer hours. What’s more, functional MRI experiments showed that
regions of the brain important for learning and memory had higher activation in
older adults who had slept more hours.
Dolphins’ diabetic turn-on
new research bolsters evidence that bottlenose dolphins go into a
harmless diabetic state that pumps up blood glucose levels during
overnight fasting. the research, presented February 18, suggests
that dolphins may be a good model for studying diabetes in people.
Most animals — but not dolphins — get their glucose fix from eating carbohydrates. “Brains need sugar to function, but a diet of fish
has no sugar,” said stephanie Venn-Watson of the national Marine
Mammal Foundation in san Diego. Blood chemistry work shows that
dolphins may have a “diabetic switch” that helps keep the brain well-fed even when they haven’t eaten for some time. in the new study,
Venn-Watson and colleagues report that the condition may become
pathological. three dolphins with abnormal insulin levels also had iron
overload, a condition associated with diabetes in people. a similar
diabetic switch may lurk in humans, she said. While humans and dolphins aren’t closely related, both have big brains and blood cells that
can move large amounts of glucose. “Maybe we can find the switch in
humans,” she said. — Rachel Ehrenberg
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