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 story the 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.