What is a sleep phase shift and what does it mean for teenagers?

Posted on 11 August 2017

A neurologist at Mediclinic explains why certain people may only fall asleep at 2am and how morning light exposure can help.

Different sleep needs

‘The number of hours of sleep that we require is dependent on the sleep needs we inherit from our parents, as well as our age. An infant may need 20 hours a day, a child or a teenager between 8 ½ and 9 ½ hours a day, and a young adult about 7 ½ hours. As we get older, our sleep needs or ability to sleep diminishes,’ explains Dr Kevin Rosman, a neurologist at Mediclinic Morningside and Morningside Sleep Centre.

What makes us sleepy at night?

‘The timing of sleep is determined by a chemical called melatonin. This, in turn, is controlled by sunlight. When we are exposed to bright light our production of melatonin is reduced, and when the light dims towards the end of the day, we experience a peak in melatonin production,’ he adds.

The average person will respond by feeling sleepy three or four hours later, at which stage they go to sleep and experience a normal night’s sleep.

However, some people will respond with a delayed response, and some people will have a completely abnormal response. So, in the lesser degrees, we see “night owls” – people who function well until late at night, and then have some difficulty getting up early in the morning – and “morning larks” – people who happily get up early in the morning, but are tired in the early evening, according to Dr Rosman.

People who only get tired very late at night and want to wake up very late in the day experience what sleep specialists term a sleep phase shift. Most commonly, this manifests into a delayed sleep phase syndrome. This is not a disease but simply means that someone may, for example, develop a natural sleep time that begins at 2am and ends at 10am.

What late nights mean for teens

In teenagers there is a tendency to develop a delayed sleep phase syndrome, although this tends to settle back in the early 20s. This is the reason why teenagers will tend to want to be up late at night, and yet sleep in whenever possible in the morning: their sleep needs remain the same, but the timing is delayed.

‘This can cause a major problem in the schooling situation. These teenagers will have great difficulty concentrating for the first couple of hours in class because they need to wake up earlier than they should wake up,’ says Dr Rosman.

Where certain schools have adapted to this, by starting classes later, dramatic improvements have been found in teenagers’ academic results according to Dr Rosman.

As a general rule, sleep phase shift problems are controlled by encouraging good sleep hygiene (good habits and routine), the use of extra melatonin as well as morning bright light exposure, amongst other techniques.

For expert assistance, contact the Morningside Sleep Centre: www.morningsidesleepcentre.com


Published in Neurology

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