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US News & World Report
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It's only 9:30 at night, but 15-year-old Ryan O. is already snuggling into bed, pulling a quilt decorated with dolphins and killer whales up over his ears. He tosses and whales and turns for several minutes before drifting off possibly because there are 12 electrodes fixed to his scalp and face and an infrared video camera is recording his every move for researchers watching a video monitor in another room.
Ryan is one of several hundred teenagers who over the past decade have
entered the twilight world of Brown University's Bradley Hospital
sleep lab, allowing sleep physiologist Mary Carskadon to record their brain waves and eye movements in
slumber and to test how lack of sleep affects their mental and physical skills. Carskadon's research has
shown that teenagers who want to sleep all day are not lazy; they are simply following the dictates of their
biological clocks.
Sleep is influenced by the circadian timing system, a bundle of
neurons, embedded deep in the brain, that regulates production of a
sleep-inducing chemical called melatonin and sets natural bedtime and rise
time. Carskadon has shown that teenagers
need more sleep than they did as children, and their biological clocks tell them to catch those extra winks
in the morning. Most teens, she says, need 9 hours and 15 minutes of sleep a night,
possibly because hormones that are critical to growth and sexual maturation
are released mostly during slumber.
That means that the average teenager's brain isn't ready to wake up
until 8 or 9 in the morning, well past the first bell at most high
schools. When Carskadon and colleagues surveyed more than 3,000 Rhode Island high school students, they
found that the majority were sleeping only about seven hours a night. More than a quarter of the students
averaged 61/2 hours or less on school nights. In another study, when students
were asked to fall asleep in the lab
during the day, many conked out within three or four minutes, a sure sign they were sleep deprived. Carskadon also discovered that the
students' melatonin levels were still elevated into the school day. "Their
brains are telling them it's nighttime," she says, "and the rest of
the world is saying it's time to go to school."
Kids who have to get up before their biological clocks have buzzed
miss out on the phase of sleep that boosts memory and learning. Periodically
during slumber, the brain enters rapid eye movement (REM) sleep, so called because the eyes dart back and forth
under the lids. During REM sleep, the brain resets chemicals in the emotional
centers and clears short-term memory banks, where the day's events are stored
temporarily. Without enough REM sleep, Carskadon and others have discovered,
people become cranky and depressed; their memory and judgment are impaired; and they perform poorly
on tests of reaction time. Carskadon has found that teens who get the least sleep earn C's and D's, while those
who get the most tend to get A's and B's. Some solutions are: q
To encourage your teen to go to bed
at a reasonable hour, keep lights low in the evening and open curtains in the morning. Light absorbed
through the eyes can reset the biological clock. q
Kids can catch up on sleep on weekends–up
to a point. Going to bed in the wee hours and snoozing until noon only disrupts the brain's clock
further. It's better to go to bed within about an hour of usual bedtime and
then sleep an hour or two later. -S.B. |
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