November 1, 2005
A new study by leading sleep experts finds that the "sleep pressure" ratethe biological trigger that causes sleepinessslows down in adolescence and is one more explanation for why teens can't fall asleep until later at night.
Published in the November issue of the journal Sleep, the study suggests that as children mature, their internal, chemically-driven pressure to sleep builds up more slowly. As a result, teens aren't sleepy until later in the evening.
"We've found another part of the storythe mechanism in the brain that builds up sleep pressure is working at a different rate in adolescents than in pre-pubescent children," says co-author Mary Carskadon, PhD, director of the Bradley Hospital Sleep Laboratory and professor of psychiatry and human behavior at Brown Medical School.
Previously, numerous studies have found that as children go through puberty, they struggle to go to bed early, a phenomenon attributed to changes in their brain's internal clock mechanics. This new finding indicates that, in addition to the changes in their internal clocks, adolescents experience slower sleep pressure, which may contribute to an overall shift in teen sleep cycles.
"The results show that the adage 'early to bed, early to rise' presents a real challenge for adolescents," says Carskadon.
The study subjects were seven pre/early pubescent children, and six mature adolescents who underwent 36 hours of sleep deprivation as their brainwaves, or electroencephalograms (EEGs) were monitored. The results showed that the build-up of sleep pressure, or sleep need, during an extended period of wakefulness is slower in adolescents than in pre-teens.
This means that for teens, the pressure to sleep doesn't kick in until later in the evening compared to younger children who have faster sleep pressure rates.
"When children are little, their sleep pressure rises faster
so they fall asleep early, but when it's slower, like it is for
teenagers, it's harder to get to sleep," says Carskadon.
The authors purport that the shift in sleep-cycles for teenagers is simply one more way to physically prepare them for full maturation.
"We propose that the higher tolerance to prolonged waking may prepare children for adult lifestyles and for performing tasks under sleep deficits that are common in adults of modern societies," the authors conclude.
The participants were recruited through newspaper ads and flyers,
and screened for sleep disorders, erratic sleep schedules, illness
and other factors known to affect sleep-wake patterns.The study
was conducted at the Bradley Hospital Sleep and Chronobiology
Journal article co-authors are: Oskar Jenni, MD, of the Bradley
Hospital Sleep and Chronobiology Research Laboratory, Brown Medical
School and University Children's Hospital Zurich; Peter Achermann,
PhD, of the University of Zurich and Mary Carskadon, PhD, of the
Bradley Hospital Sleep and Chronobiology Research Laboratory,
and Brown Medical School, where the research was performed.