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Last week, Radio NZ interviewed Dr Paul Kelley, an educational researcher from the UK, on educational outcomes in adolescents when school timing is shifted to a later start time.  From a sleep science point of view, I wasn’t blown away by Paul’s interview and I was surprised that Radio NZ had opted to not to describe any of the New Zealand research that had been done.  So I thought I would…

Both local and international research has shown that teenagers get less than the optimal amount of sleep.  This has a number of implications.  Sleep loss in teenagers is associated with weight gain, substance use, motor vehicle accidents, low self-esteem and poor academic outcomes.

Noticeable changes are seen in sleep and circadian (body clock) biology during adolescence.  Not only does the structure of our sleep change, but the timing of our circadian clock shifts later relative to the day/night cycle.  That is, teenagers have a biological shift to later bed times and wake times relative to the start of the waking day, which is more pronounced in older teenagers.

We see a distinct difference in total sleep time between school and non-school days that is partly due to this biological change in the circadian clock.  Teenagers who try to go to bed at a time that allows them get enough sleep before school may find it difficult to get to sleep.  On school days, when they are required to wake early, their sleep may be cut short.

However, the shift to later bed and wake times is a little more complex than a pure biological shift in the circadian clock.  There are a number of psychosocial and behavioural factors which contribute to this sleep pattern.  For example, there is often increasing autonomy in use of technology, ‘screen’ time and social interaction during adolescence.  The stimulating nature of these activities may mean that bed time is pushed later.  In addition, exposure to bright light (screens), and in particular blue-enriched light, during the evening can have an effect on the timing of our circadian clock.

During the recent Radio NZ interview, Paul Kelley described changes he had helped initiate in UK schools to shift school start times later, in order to improve opportunity for sleep.  Here in New Zealand, Wellington High School independently decided to make similar changes in 2006.  Years 12 and 13 students at Wellington High School start school at 10.30am.

This change in school start times at Wellington High School was prompted by the findings of a pilot study conducted by Brigid Borlase at the Sleep/Wake Research Centre, who had examined sleep issues in Wellington High School students in 1999.  Brigid also conducted a follow-up study in 2008 to assess the impact of the change in school start time by comparing Year 12 students from 2008, with Year 12 students from 1999 and Year 11 students from 2008 (with a 9am start time).

In 2008;

  • late start students got more sleep, were less sleepy and were less likely to say they missed out on sleep than early start students from 1999 or 2008
  • late start students were more likely to report that it was easy for them to get up in the morning and that they felt ok on waking
  • early start students were more likely to report missing out on sleep on school nights than late start students
  • students who had more technology the bedroom slept less

There are limitations to this study.  The study relied on self-reports from the students.  It is not known how these findings relate to academic outcomes, but anecdotal reports from the teachers at Wellington High School suggest that students are more alert, responsive and engaged in the classroom.  There have also been significant changes in technology between 1999 and 2008, which was reflected in a substantial increase in the number of students with technology in the bedroom (81% in 1999; 96% in 2008).  This study did not capture the amount of time spent using these devices, or when they were used.  The study findings hinted that these students were using the extra time available for sleep.  They didn’t appear to be shifting their bedtimes any later, but were waking later in the morning.  It would be great to capture the specific changes adolescents make in their sleep behaviour alongside interventions like this.