Sleep - everything you always wanted to know but were too tired to ask

Updated: Feb 16, 2019

How much sleep do I need?

National Sleep Foundation guidelines:

  • School age children (6-13): 9-11 hours

  • Teenagers (14-17): 8-10 hours

  • Adults (18-25): 7-9 hours

When should I fall asleep?

This depends a lot on when you need to get up. You should look at when the alarm clock is set and work backwards to ensure a minimum 8 hour sleep opportunity. For example, if you have to get up at 6am, the latest you should be falling asleep the previous evening is 10pm. That probably means actually going to bed another half hour earlier, at 9.30pm.

That said, there is evidence that getting to sleep earlier is associated with academic success at university. US students getting the highest Grade Point Average scores have significantly earlier bedtimes and rise times than those with the lowest scores, even when total sleep time is no different.

The National Sleep Foundation provides further advice on when young people should be able to fall asleep:

  • 6 to 11 year-olds: about 7:30 pm to 9pm

  • Teenagers: about 9pm to 10:30pm

To nap or not to nap?

If you are getting less than the minimum 8 hours, regular napping may reduce the harmful effects. However, you need to be careful because a long nap will make it harder to get to sleep at night, potentially creating a vicious cycle of nighttime sleep deprivation and daytime napping.

A power nap of just 10 minutes at about 3pm is the best way to catch up on a sleep-deprived night. There are some practical issues here - the 10-minute timing can be carefully controlled in a sleep lab but is more difficult at home. It's likely that setting an alarm for around 20 minutes is likely to give you the most chance of hitting the 10-minute optimum sleep you need.

But keep in mind that getting the full 8+ recommended hours of nighttime sleep should be the priority.

Am I getting quality sleep?

There are a number of ways that researchers measure sleep quality. The first is to identify the number of times you wake during the night. More than one wake-up during the night will affect sleep quality (this is known as sleep fragmentation). Basically, the more sleep fragmentation you have during the night, the more sleepy you'll feel the next day and the less effective you'll be at any tasks requiring concentration.

A second key indicator is variability in the length of nighttime sleep across consecutive nights. Good quality sleep is characterised by getting about the same number of hours of sleep each night, ideally starting and ending at about the same time.

Finally, 5 sleep tips from a professor of neuroscience

If you snooze you lose, right?

Wrong. What you will notice, if you start taking Professor Matthew Walker's recommendations seriously, is that there's a lot of bravado - in our productive-conscious societies - about how clever it is to function on very little sleep.

If you are ever confronted with someone who is even hinting at looking down on you for needing more sleep, point them in the direction of the evidence which shows that less than 8 hours will make them uglier, and fatter, and more stupid. If they are male you could also throw in the fact that it will lead to a lower sperm count and smaller testicles. If they are still sceptical, point out that less than 8 hours of sleep is associated with higher risk of depression, anxiety, cancer, dementia, stroke, heart attack and diabetes.

Some people will point to high-achieving non-sleepers such as former US president Ronald Reagan and former UK prime minister Margaret Thatcher – they both died of dementia which has a much higher risk if you are sleep deprived.

If, after all this, you find someone who is still sceptical about the importance of sleep – best to let them know that they are displaying the kind of irrational thought processes which are a sure sign of sleep deprivation.