Now more than half way into the school term, pubescent children will be showing signs of wear and tear. A significant factor is the grim discrepancy between school hours and the natural sleep rhythms of most teenagers. Studies from many nations show that normal school hours have a baleful impact.
In puberty we tend to become "evening people", preferring later bed and waking times. This has a biological basis, with melatonin secretion (a key hormone in wakefulness) delayed in teens compared with pre-teens. The list of adverse effects associated with reduced and irregular sleep is long, with depression, increased accidents, more drug use and worse school performance being only some of them. During holidays they sleep longer and get up later.
Of course, individuals vary in the extent to which they are morning or night people. Children who naturally go for evenings are particularly at risk of, in effect, feeling jet-lagged by the school schedule. A study of 310 Australian 15-18-year-olds demonstrated just how severe the effects can be, comparing sleep patterns during two fortnights – holiday versus term-time.
Overall, the teens averaged 55 minutes less sleep a night during the school term compared with the holidays. In both the holidays and school terms, students reported that they ideally needed about eight hours 45 minutes' sleep. This was exceeded during the holidays, with students sleeping for nine hours 12 minutes on weeknights – a sleep credit. During school term they averaged just under eight hours a school night, running up considerable sleep debts.
On school nights (Sunday to Thursday), the sample slept significantly less (an average of 77 minutes) than the same weeknights over the holiday period, despite going to bed earlier.
On school mornings (Monday to Friday), students reported waking up an average of two hours 34 minutes earlier than they did during the holidays. They obtained 1 hour 22 minutes less sleep a night than they believed ideal for them. Although they slept longer at weekends during term time, it was nowhere near enough to pay back the sleep debts run up during weekdays.
You can see where your child fits in from the extremes. During the holidays, the lowest reported average sleep was four hours 11 minutes a night, the highest 13 hours 31 minutes; but only 6% of the sample had less than seven hours' sleep a night. During school term, average sleep ranged from a low of three hours 51 minutes a night to a high of 10 hours 55 minutes, with 15% reporting less than seven hours: over twice as many children were getting less than seven hours a night during term time. Boys were slightly more prone to be night owls than girls.
Sure enough, sleep deprivation predicted more negative mood and poorer daytime academic performance and behaviour during term time, especially among children who were particularly prone to be night owls. For them, the early start time of schools is very unhelpful.
The implications are considerable. Just as it suits hospital rotas to wake patients early regardless of their condition and personal time clock, designed to suit staffing issues, so school timetables are arranged to suit parents, teachers and businesses. It is true that it would be tricky to design a system that enabled teens to start school at 10am or later. But that is clearly what is required.
Short of home-educating (not an option or wish for most parents), where you could start their day at a time that fitted their circadian rhythm, there is not much you can do to solve this problem. But at least now you know that the sluggish morning behaviour of your morose teen is neither laziness nor your fault.
Holiday and School-Term Sleep Patterns of Australian Adolescents: Warner, S et al, 2008, Journal of Adolescence, 31, 595–608
