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Published: 30 May 2017

Delaying school start times won’t help sleep-deprived teenagers

Delaying school start times in the UK is unlikely to reduce sleep deprivation in teenagers, research from the University and Harvard Medical School has found.

The research, conducted in collaboration between mathematicians and sleep scientists, predicts that turning down the lights in the evening would be much more effective at tackling sleep deprivation.

Teenagers like to sleep late and often struggle to get up in time to go to school. The commonly accepted explanation for this is that adolescents’ biological brain clocks are delayed. It has been suggested that to remedy this, school start times should be delayed for older teenagers so that they are in tune with their biological clock. 

The study used a mathematical model that takes into account whether people are naturally more of a morning or evening person, the impact of natural and artificial light on the body clock and the typical time of an alarm clock, to predict the effects of delaying school starts.

The mathematical model showed that delaying school start times in the UK would not help reduce sleep deprivation. Just as when clocks go back in the autumn, most teenagers’ body clocks would drift even later in response to the later start time, and, in a matter of weeks, they would find it just as hard to get out of bed. The results did, however, lend some support to delaying school start in the US, where many schools open as early as 7am.

The research found that the problem for adolescents is that their light consumption interferes with the natural interaction with the environmental clock – getting up late in the morning results in teenagers keeping the lights on until later at night, which delays the biological clock, making it even harder to get up in the morning. The mathematics also suggests that the biological clocks of adolescents are particularly sensitive to the effects of light consumption.

The study suggests that an alternative remedy to moving school start times in the UK is limiting exposure to bright light during the day, and turning the lights down in the evening and off at night.  For very early start times, as in some US regions, any benefit gained from delaying school start times could be lost unless it is coupled with strict limits on the amount of evening artificial light consumption.

Lead author Dr Anne Skeldon, of the Department of Mathematics, said: “The model highlights that adolescents are not ‘programmed’ to wake up late and that increasing exposure to bright light during the day, turning lights down in the evening and off at night should enable most to get up in time for work or school without too much effort and without changing school timetables.”

Co-author Prof Derk-Jan Dijk, Director Surrey Sleep Research Centre, said: “Just as mathematical models are used to predict climate change, they can now be used to predict how changing our light environment will influence our biological rhythms.

“It shows that modern lifestyles make it hard for body clocks to stay on 24 hours, which shifts our rhythm of sleepiness and alertness to later times – meaning we are sleepy until late in the morning and remain alert until later in the evening.

“As a result, during the working week our alarm clocks go off before the body clock naturally wakes us up. We then get insufficient sleep during the week and compensate for it during the weekend.  Such patterns of insufficient and irregular sleep have been associated with various health problems and have been termed ‘social jet lag’.”

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