Chris Idzikowski (Director of the Edinburgh Sleep Centre) gives expert video advice on: Why do we need sleep?; How much sleep is recomended each night?; Does the amount of sleep differ between men and women? and more...
Why do we need sleep?
It is clearly to rest and recover and that's probably as far as it goes. There are various theories around. Most of them either cover recovery... Others cover perhaps preventing us walking around in the dark and bumping into things because we are not adapted to living in that type of environment. So; two classes of theories.
How much sleep is recomended each night?
The recommendation varies between person to person; whether he is a deep breather or shallow breather, the best index is that if that your heart feels refreshed after a sleep a little less sleep is ok.
Does the amount of sleep differ between men and women?
Sometimes it's said that women may sleep less than men, but really the large statistical surveys tend to point to roughly equivalent or perhaps even more with women. I think it's really just highly variable, so I don't know what the sex differences are. When one gets sleep disorders, like insomnia, there tends to be a difference between men and women.
Is it dangerous to have too much sleep?
No, there's no indication that too much sleep per se is a problem. If anything, the more one sleeps the better is one's mental performance and that's the way it seems to go. If on the other hand, you've got uncontrollable sleep and you're sleeping a lot, then the question is "why is that happening?"
What are ciradian rhythms?
Circadian rhythms are defined as biological rhythms that run every 24 hours and that's opposed to ultradian rhythms that are faster than 24 hours or infradian rhythms that run longer than 24 hours. But basically its a 24 hour cycle and sleep and wakefulness is a 24 hour rhythm
Can you explain the stages of sleep?
The way a normal night occurs is you go into drowsy sleep, then into light sleep, then very quickly into deep sleep. It was called slow wave sleep because that's the way it looked when you were looking at brain waves; or stages 3 and 4 sleep. Nowadays we've lumped it all into calling it deep sleep. You then lighten a little bit and you go into rapid eye movement sleep; dreaming sleep. You have some of that, and then you go back into deep sleep, then some more rapid eye movement sleep, then the light sleep generally. And then more rapid eye movement sleep. The sleep itself is punctuated by an ultradian rhythm; by a 90 minute rhythm. So roughly every 90 minutes you go into rapid eye movement sleep. So for the whole night you'd get something like; 25% of the night would be deep sleep, 25% of the night would be dreaming sleep, but half the night would be light sleep. But the way it would be punctuated would be this 90 minute cycle. Predominantly deep sleep at the beginning of the night; predominantly rapid eye movement or dreaming sleep at the end of the night.
What is REM?
Rapid eye movement sleep was originally called paradoxical sleep. The reason it was called that was when people were first investigating sleep by putting electrodes on, they found there was a stage where the brainwaves looked as if the person was awake or drowsing. Their muscles were paralyzed but their eyes were darting about as if they were looking at something. If you woke them up at that point, you would find that they were dreaming. Because of those rapid eye movements, it was called rapid eye movement sleep. It was also called paradoxical sleep because of this mismatch between muscle paralysis and being asleep with this apparent active brainwave activity.
How do we know when we need sleep?
What drives sleep is how long one has been awake. We suspect that various compunds in the brain accumulate to the point where they're trying to drive the brain along and get it into a state of sleep. But you have to be in a situation where sleep is appropriate and also the biological clock has to agree that it's the right time, so you get this mixture of things going on. But the thing to always keep in mind is the pressure for wakefulness which drives the pressure for sleep and what the biological clock is saying which will enable sleep to happen.
Is sleep good for you?
Sleep is absolutely vital for good functioning, but there is another side to sleep. Peak mortality occurs around eight in the morning but it starts to increase from around four in the morning. We're not entirely sure what's going on, but part of the reason may be that the blood comes a little bit thicker during sleep because we are not moving around as much. And also, as the end of the night tends to be rapid-eye movement sleep where a lot of the physiology is less regulated than it usually is, one gets more extremes as the heart rate can go up and down and whatever. The combination of all these things leads to more heart attacks and strokes around the time of awakening in an hour or two later.
Is sleeping different for blind people?
Yes, sleeping can be different for blind people . . . so one of the things about the biological clock is it's controlled hugely by light. And the biological clock normally runs slowly; dawn light speeds it up every day. If one's blind and there's no information going into the biological clock, then that reset doesn't occur, so their clocks slowly drift during the day. Which means they can be sleeping well during the night to start with, but a day later they'll be going to bed slightly later and waking up slightly later. A fortnight later they could be sleeping well during the day but they can't sleep during the night. A fortnight later they'll be sleeping well during the night again, not during the day, so that reset's not occurring. So a lot of blind people will suffer from insomnia. It's not really insomnia because the biological clock isn't sticking to the right time for them.