We asked sleep expert Russell Foster, Professor of Circadian Neuroscience at Oxford University, to answer some of the most frequently asked questions about our all-important shut-eye
Do we all need eight hours of sleep?
That's sort of the scream that you get from the sergeant majors of sleep. It's one of the reasons I wrote my book, 'Lifetime', because it's nonsense. I mean, that may be the average. But in fact, healthy sleep can range from six hours to ten, maybe even 11 hours. And so it's like shoe size, trying to make everybody wear the same shoe size is like everybody having to have the same sleep pattern. It's very, very different.
Is blue light before bed really a problem?
Well, the sort of light and levels of light you get from computer screens or tablets or phones and things that isn't really bright enough to have much of an effect. So I don't think we should be worrying too much about blue light.
Clearly, if the light is bright, actually whatever colour or wavelength, it can increase alertness and delay sleep. But the sorts of levels you're getting from most devices, there's no real evidence that it will impact upon our sleep or circadian rhythms.
Is it a bad sign if you wake up in the night?
It looks like the default pattern for human sleep is very much to wake up and then go back to sleep again. Most of us are unaware that we've woken up. But if you do wake up in the middle of the night, it's nothing to worry about. If you stay relaxed and calm, you will get back to sleep.
What should you do if you can’t get back to sleep?
So the tricks, if you do wake up. Of course. It's about staying calm. You may want to stay in bed and just if you're relaxed. Other people are very keen to sort of get out of bed. Have a few pages of Jane Austen on their Kindle or whatever, and that as soon as you feel tired, you can go back.
I will listen to some radio for extra. And I have to say that Melvyn Bragg, in our time, does it for me. I love the programs, but it's so relaxing and gentle that it helps me get back to sleep.”
Does when we eat affect our sleep?
So the overwhelming evidence is to concentrate one's calorie intake during the first half of the day. Breakfast and lunch, and have a light supper.
Circadian rhythms are sort of geared up to process food during the first part of the day. And so what you see is if you give somebody a constant infusion of glucose, you see that glucose is taken out of circulation quickly during the first half of the day, but before bed it can hang around a long time and of course it's not being used up. And so it's led to deposits such as glycogen in the liver or fat. So very much concentrate your calorie intake during the first half of the day.
Does alcohol help you sleep?
A drink before you go to bed can be relaxing. But if you're using alcohol to get to sleep, you're not getting sleep. You're getting sedation. And it can actually be harmful to some of the important things going on within the brain whilst you sleep, like memory formation and the processing of information to come up with novel solutions to complex ideas. So don't use alcohol as a sedative. It's a really bad idea.
Is it okay to nap?
I think sleep is a very complicated behaviour, so I wouldn't put any strong rules of do and doubt. An occasional nap less than 20 minutes. Less than 30 minutes is probably fine.
The danger about naps is if they become longer and if they're close to bedtime. If they're longer, you can fall into a deeper sleep. And so recovery from that deeper sleep can leave you groggy. But if you're also close to bedtime, that can be a problem because it pushes back the sleep pressure.
Occasional nap? Fine. If you become dependent on them to get through the day, that's when I start to get a little uneasy.
How do I know how much sleep I need?
How long your body tells you you need to sleep. And it's all about can I function optimally during the day? Do I need to oversleep on three days? This is all telling you that you are, or you're not getting the sleep that you need. And it's all about finding what works for you and then sticking to it.
How do I know if I’m not getting enough sleep?
Are they saying you seem to be overly impulsive? You don't seem to be as reflective. You don't seem to have the same sense of humour. You're not as empathetic. You are showing higher degrees of anger. These are absolutely characteristic of not getting enough sleep.
And if you notice in yourself you're doing stupid and unreflective things. Impulsive things. Things you wouldn't do if you were fully rested. It's about listening to others and also having the courage to listen to yourself.
What’s the best way to relax before bed?
De-stressing comes in a whole variety of different forms. There's some beautiful data showing that mindfulness for some people can be a fantastic relaxation technique.
For others it's going to the gym, not too close to bedtime. It may be listening to a wonderful piece of music. My sleep patterns improve enormously when the Proms are on. It may be just winding down and reading a few pages of your favourite novel. It's about finding those relaxation techniques that work for you.
