Teens may be hardwired to sleep in

By Peter Woodford

According to Dr Mary Carskadon, a psychiatry and human behaviour professor at Brown University and an authority on circadian rhythms, typical North American teens get just 7.5 hours of sleep during school nights and about a quarter only get 6.5 or fewer hours of sleep. About half the teens who show up for school show many of the symptoms similar to narcolepsy purely as a result of their insufficient time with the Sandman. Complicating matters further is that many ? even severely exhausted ? teens' circadian rhythms give them a late-night second wind so they often don't get tired until 1am, robbing them of yet more precious slumber.

WEEKEND SLUMBER BENDERS
Teens usually cut down this formidable sleep deficit through weekend 'binge sleeping.' Dr Carskadon acknowledges the importance of catching up on lost ZZZs but warns it can play merry hell with a teen's sleep cycles. "The brain is getting very different messages about when nighttime is," she says. Though this sentiment would get most parents' approval, not all experts agree. Dr Carlyle Smith, a Trent University professor of psychology and sleep researcher, is an enthusiastic supporter of letting teens sleep in on weekends. Parents should let their teenage kid sleep in, he says, but many of them don't realize that sleep requirements for teens are as high as preteens.

It's also believed that adolescent culture's pull (internet use, late-night TV, cell phone texting, etc) is amplifying circadian-driven teenage tendencies to stay up late. School, of course, forces teens to get up early. For some experts, early secondary school start times (commonly 8am in Canada) are partly to blame for the huge teenage sleep deficit.

RHYTHM OF THE NIGHT
Circadian rhythms are rarely considered when we schedule events for teens. University of San Diego psychiatry professor Dr Sonia Ancoli-Israel favours a more scientific approach to secondary school timetables. "We have to understand that teens all have different patterns of sleep just as adults do," she says, "so what is ideal for one teen may not be ideal for another. But in general, starting high school at around 8:30 or nine o'clock would help many."

Delaying first bell isn't without problems. It forces many working parents to hire sitters to look after younger children, and cuts into extra-curricular activity time. But if those pushing for later school start times are right, we as a society may well be mortgaging our future just to keep the status quo. Teens running on empty in the early morning have acutely impaired mental and physical reaction times. They just aren't learning, and in many cases are driving themselves to school in a dangerous state.

In the US, there have been some bold initiatives to tackle the problem from the school start time front. A University of Minnesota study had some of the state's school boards experiment with pushing the first bells up from before 7:15am to 8:40am. Results were very encouraging, particularly for students who were on the verge of dropping out. For example, the percentage of 10th-graders who stayed enrolled went from 55% in 1995-96 to 67% in 1999-2000.

For Dr Ancoli-Israel there's still a big role for physician and parental counsel. "I think that circadian rhythms definitely need to be taken into consideration, but the behavioural approach is also important ? for example, we should encourage limiting teens' late night TV." Dr Carskadon concurs and offers these tips for parents: "Provide a bedtime for adolescents, turn off the power in the evening and turn it on in the mornings. Bright lights and activities in the morning and dim or no lights in the evening send the correct nighttime message to the brain."

For more information see Dr Carskadon's editorial in June's Archives of Pediatrics & Adolescent Medicine.