Why teenagers need more sleep

时间:2018-01-23 单词数:5560

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In the UK, the clocks go back by one hour on Sunday to mark the end of British Summer Time. Experts have been weighing up a more permanent time shift in our daily schedules, particularly for tired teenagers who struggle with early school starts.


The rethink on teen slumber is largely due to the emerging science on circadian rhythms. The genetics associated with body clocks earned this year’s Nobel Prize for physiology or medicine. The timing of release of the sleep hormone melatonin is thought to change with age: during adolescence, secretion begins late at night and continues until about 8am. The sleep rhythm of a teenager can lag an adult by two to three hours.


A report by the Rand Corporation argues that, for adolescents, delaying the start of school to 8.30am or later could bring a $140bn benefit to the US economy over 15 years. Some US school days start as early as 7am.


The gains, which amount to a dividend of $9.3bn a year, arise mainly from two predicted pay-offs: improved academic performance, which increases the likelihood of graduation and future work; and a reduction in car crashes, which means more students make it into the future labour supply.


Marco Hafner, a Rand economist, says the gains could be even higher because the calculation of benefits were on the conservative side. The input to the macroeconomic simulation did not factor in other phenomena, such as the risks of suicide and obesity that are believed to be exacerbated by sleep deprivation.


Rand, which used data from 47 US states, concluded that teenage sleep deprivation should be regarded as an economic problem with a possible solution. The financial rewards, it says, would quickly outweigh any associated costs of fixing it, such as rescheduling bus routes or extending after-school clubs.


A similar debate has been stirring in the UK. In 2015, Paul Kelley, a professor at the Sleep and Circadian Neuroscience Institute at Oxford university, suggested that 16-year-olds should start no earlier than 10am. For 18-year-olds, an 11am start is preferable. Early starts, he says, mean pupils are usually performing suboptimally.


Not everyone concurs: scientists at the universities of Surrey and Harvard dispute that delayed starts will lead to teenagers getting more sleep. One unintended consequence, for example, might be students being exposed to artificial light for longer because of later bedtimes.


Based on mathematical modelling, this contrary study suggested that turning down the lights in the evening would allow teenagers to get more sleep without the need for a change to the school day. The time that students spend on their mobile phones and other devices also crops up regularly as a complicating factor in teenage sleep studies.


Nevertheless, one London head of an independent school has chosen to push back the start of the day for sixth-formers to 9.30am. Explaining his decision in an article for the Times Educational Supplement, Jonathan Taylor pointed out that the 9-to-5 mode of working was disappearing anyhow. He criticised educators who clung to an early start out of “a misguided notion of traditional self-discipline?.?.?.?is it really more worthy to learn maths at 8.30am than 5pm?”


Attendance and punctuality, Mr Taylor enthused, had improved – and the teenagers made for jollier company. Heaven knows, we could all do with happier teens.