People And Sleep

Why do some people need more sleep than others?

We have no idea why these individual differences really arise. Why one can have short sleepers or long sleepers. One question you asked earlier was how much sleep do we need? If one takes the population average, we'd say that most people sleep about seven and a half hours during the night, then plus/minus 2 hours. So a range of five and a half to nine and a half hours will still encompass a huge chuck of the population. It isn't until you move further out that you're down to the three, three and a half hour REM set. That's really quite unusual. But why the differences emerge we're not sure.

Do children or adults need more sleep?

Babies and children sleep more than adults do. And in fact we may well be born into the world in asleep and it's a rude shock when get in. The fact that babies and children sleep more than adults has been used as evidence that sleep has a restorative, recovery, or growth function.

Do elderly people need more sleep?

Its hard to generalize, we used to say quite a lot that elderly people slept less than everybody else. And then it turns out that healthy elderly people could be good sleepers, and as good as they were in their thirties and forties. If somebody is particularly sleepy at any time then it implies that there is a sleep disorder going on somewhere that is causing problems with the sleep being recuperating and thus likely petering during the day. It is also hard to generalize at all. Elderly tend to accumulate more and more disorders and more and more ailments and more difficulties in actually staying asleep so they end up with less sleep but that doesn't necessarily mean that they don't need it.

Why do children and elderly people fall asleep very easily?

If somebody can't control their wakefulness because they're falling asleep and they just can't manage it, it implies that there's a sleep disorder going on. Now with youngsters and children it could just be the fact that they need a bit more sleep. They haven't got enough during the night. With adults it might be more along the lines of something that's going wrong with their sleep and that needs to be investigated.

Why do children often wake in their sleep?

Certainly their cycle of awakening is shorter then an adult's. So the odds of an adult being awoken out of their sleep are high if children are running at 50 minutes and the adults are running at 90 minutes. But there is no strong reason why there should be a large number of awakenings other than discomfort or ailments or whatever.

Do all mammals have the same sleep pattern?

There's a huge variety of sleep across all mammals. So some mammals are nocturnal, they're active at night and sleep during the day. Most mammals in fact have highly disturbed and distributed sleep so a nocturnal mammal will also sleep during the night as well as being active during the night. Humans are almost the only mammal that tries to consolidate all of their sleep into one particular time. And even there, with the siesta cultures one doesn't see that. In fact if one goes back to the 19th century and looks at shepherding cultures, there they have a more distributed sleep pattern then we would regard as reasonable nowadays. So they're both different patterns of sleep. And also the biological clock runs at a different rate so the ultradian rhythm, the nineteen minute cycle that one sees within sleep is hugely faster in small brain species like mice and rats than in large brain species like dolphins and mammals. And it gets more complicated, if you look at dolphins and porpoises, so aquatic mammals, they in fact have a mechanism whereby one half of the brain goes to sleep whilst the other half remains awake and vice versa, and there's a cycle there as well.

Are we aware of our surroundings when we sleep?

The brain's analyzing information all the time, even when we are asleep. And making decisions as to whether we should awaken or not and attend to the sounds. An example of that is thinking about how a baby's whimper will invariably awaken a parent whereas a snorer who can generate industrial levels of noise won't awaken themselves. Another example of that is, if you're in dreaming sleep, and experimentally provide somebody with emotionally salient material, then it will get incorporated into their dream. An example might be something like if you provide the name of somebody's parent, that parent will then probably arise in the dream so you let them dream for ten, fifteen minutes, and you awaken them and they'll tell you about it.