Myth Conceptions
The Age
Saturday February 10, 2007
You may think that the infinite ability of teenagers to sleep in on weekends is all down to attitude, but this altered sleep pattern isn't about being bone-lazy or antisocial, it's about biology.
Newborn babies sleep, in a series of naps, for 16 to 18 hours a day. By age five, this is down to about 11 hours, and continues to drop with age - until puberty starts. Puberty lasts to about 17 years and five months in boys, and 16 years in girls, as measured by the end of bone growth. But adolescence continues for a few more years.During adolescence, the natural circadian rhythm is mightily interfered with and there is a delay in the onset of sleep, probably due to the later release of melatonin. So a teenager claiming to be not tired at 11pm is probably being truthful. Another biological change is that adolescents need more sleep - between nine and 10 hours every night. Indeed, one marker of the end of adolescence is the switch to the shorter and earlier adult sleep hours. This happens, on average, at 19 years and five months in women, and 20 years and nine months in men.The teenage years are very messy, in terms of sleep. An early bedtime is, in most cases, simply fighting biology. Adolescents need nine to 10 hours of sleep, but often start school early. Typically, an adolescent, going from holidays to regular school, will sleep for two hours fewer on weeknights, and try to make it up on weekends. So your average high-school student sleepwalks through their school day, in a semipermanent state of sleep deprivation. Various studies have shown that this sleep deprivation is linked to rebellious behaviour, depressive symptoms, cigarette smoking, obesity, anxiety disorders and poor school marks. Indeed, being tired while taking an IQ test can drop about seven points off your score - and can do the same for regular exams. Also, about 20 per cent of road deaths are caused by microsleeps related to tiredness - and about half of all such fatigue-related road deaths happen to those aged 16 to 25. Another study looked at so-called REM sleep, during which humans do most of their dreaming and which usually happens about 70 to 100 minutes after falling asleep. About half of the high-school students studied were so tired that, when given the opportunity to sleep at school in mid-morning, they dropped into REM sleep within a few minutes. So what can help? Well, adolescents should avoid caffeinated drinks and not have a computer or TV in their bedroom. Dr Martin Ralph, a psychologist at the University of Toronto, recommends starting university and high-school classes at 11am. And next time you want to chide your teenager with a well-worn cliche, in the interests of scientific credibility don't make it, "Early to bed and early to rise ..."
© 2007 The Age