Russell Foster: Why do we sleep? (2)
One of the things that the brain does is indulge in micro-sleeps, this involuntary falling asleep, and you have essentially no control over it. Now, micro-sleeps can be sort of somewhat embarrassing, but they can also be deadly. It's been estimated that 31 percent of drivers will fall asleep at the wheel at least once in their life, and in the US, the statistics are pretty good: 100,000 accidents on the freeway have been associated with tiredness, loss of vigilance, and falling asleep -- a hundred thousand a year. It's extraordinary. At another level of terror, we dip into the tragic accidents at Chernobyl and indeed the space shuttle Challenger, which was so tragically lost. And in the investigations that followed those disasters, poor judgment as a result of extended shift work and loss of vigilance and tiredness was attributed to a big chunk of those disasters. When you're tired and you lack sleep, you have poor memory, you have poor creativity, you have increased impulsiveness, and you have overall poor judgment. But my friends, it's so much worse than that. (Laughter)
If you are a tired brain, the brain is craving things to wake it up. So drugs, stimulants. Caffeine represents the stimulant of choice across much of the Western world. Much of the day is fueled by caffeine, and if you're a really naughty tired brain, nicotine. Of course, you're fueling the waking state with these stimulants, and then, of course, it gets to 11 o'clock at night, and the brain says to itself, "Actually, I need to be asleep fairly shortly. What do we do about that when I'm feeling completely wired?" Well, of course, you then resort to alcohol. Now alcohol, short-term, you know, once or twice, to use to mildly sedate you, can be very useful. It can actually ease the sleep transition. But what you must be so aware of is that alcohol doesn't provide sleep. A biological mimic for sleep, it sedates you. So it actually harms some of the neural processing that's going on during memory consolidation and memory recall. So it's a short-term acute measure, but for goodness sake, don't become addicted to alcohol as a way of getting to sleep every night. Another connection between loss of sleep is weight gain. If you sleep around about five hours or less every night, then you have a 50 percent likelihood of being obese. What's the connection here? Well, sleep loss seems to give rise to the release of the hormone ghrelin, the hunger hormone. Ghrelin is released. It gets to the brain. The brain says, "I need carbohydrates," and what it does is seek out carbohydrates and particularly sugars. So there's a link between tiredness and the metabolic predisposition for weight gain: stress. Tired people are massively stressed. And one of the things of stress, of course, is loss of memory, which is what I sort of just then had a little lapse of. But stress is so much more. So, if you're acutely stressed, not a great problem, but it's sustained stress associated with sleep loss that's the problem. Sustained stress leads to suppressed immunity. And so, tired people tend to have higher rates of overall infection, and there's some very good studies showing that shift workers, for example, have higher rates of cancer. Increased levels of stress throw glucose into the circulation. Glucose becomes a dominant part of the vasculature and essentially you become glucose intolerant. Therefore, diabetes 2. Stress increases cardiovascular disease as a result of raising blood pressure. So there's a whole raft of things associated with sleep loss that are more than just a mildly impaired brain, which is where I think most people think that sleep loss resides. So at this point in the talk, this is a nice time to think, "Well, do you think on the whole I'm getting enough sleep?" So a quick show of hands. Who feels that they're getting enough sleep here? Oh. Well, that's pretty impressive. Good. We'll talk more about that later, about what are your tips. So most of us, of course, ask the question, "How do I know whether I'm getting enough sleep?" Well, it's not rocket science. If you need an alarm clock to get you out of bed in the morning, if you are taking a long time to get up, if you need lots of stimulants, if you're grumpy, if you're irritable, if you're told by your work colleagues that you're looking tired and irritable, chances are you are sleep-deprived. Listen to them. Listen to yourself.
What do you do? Well -- and this is slightly offensive -- sleep for dummies.
Make your bedroom a haven for sleep. The first critical thing is make it as dark as you possibly can, and also make it slightly cool. Very important. Actually, reduce your amount of light exposure at least half an hour before you go to bed. Light increases levels of alertness and will delay sleep. What's the last thing that most of us do before we go to bed? We stand in a massively lit bathroom, looking into the mirror cleaning our teeth. It's the worst thing we can possibly do before we go to sleep. Turn off those mobile phones. Turn off those computers. Turn off all of those things that are also going to excite the brain. Try not to drink caffeine too late in the day, ideally not after lunch.
Now, we've set about reducing light exposure before you go to bed, but light exposure in the morning is very good at setting the biological clock to the light-dark cycle. So seek out morning light. Basically, listen to yourself. Wind down. Do those sorts of things that you know are going to ease you off into the honey-heavy dew of slumber.
OK. That's some facts. What about some myths?
Teenagers are lazy. No. Poor things. They have a biological predisposition to go to bed late and get up late, so give them a break.
We need eight hours of sleep a night. That's an average. Some people need more. Some people need less. And what you need to do is listen to your body. Do you need that much or do you need more? Simple as that.
Old people need less sleep. Not true. The sleep demands of the aged do not go down. Essentially, sleep fragments and becomes less robust, but sleep requirements do not go down.
And the fourth myth is early to bed, early to rise makes a man healthy, wealthy and wise. Well, that's wrong at so many different levels. (Laughter)
There is no evidence that getting up early and going to bed early gives you more wealth at all. There's no difference in socioeconomic status. In my experience, the only difference between morning people and evening people is that those people that get up in the morning early are just horribly smug.
OK. So for the last few minutes, what I want to do is change gears and talk about some really new, breaking areas of neuroscience, which is the association between mental health, mental illness and sleep disruption. We've known for 130 years that in severe mental illness, there is always, always sleep disruption, but it's been largely ignored. In the 1970s, when people started to think about this again, they said, "Yes, well, of course you have sleep disruption in schizophrenia, because they're on antipsychotics. It's the antipsychotics causing the sleep problems," ignoring the fact that for a hundred years previously, sleep disruption had been reported before antipsychotics. So what's going on? Several groups are studying conditions like depression, schizophrenia and bipolar and what's going on in terms of sleep disruption. We have a big study which we published last year on schizophrenia, and the data were quite extraordinary. In those individuals with schizophrenia, much of the time, they were awake during the night phase and then they were asleep during the day. Other groups showed no 24-hour patterns whatsoever -- their sleep was absolutely smashed. And some had no ability to regulate their sleep by the light-dark cycle. They were getting up later and later and later and later each night. It was smashed.
So what's going on? And the really exciting news is that mental illness and sleep are not simply associated, but they are physically linked within the brain. The neural networks that predispose you to normal sleep, give you normal sleep, and those that give you normal mental health, are overlapping. And what's the evidence for that? Well, genes that have been shown to be very important in the generation of normal sleep, when mutated, when changed, also predispose individuals to mental health problems. And last year, we published a study which showed that a gene that's been linked to schizophrenia, when mutated, also smashes the sleep. So we have evidence of a genuine mechanistic overlap between these two important systems.
Other work flowed from these studies. The first was that sleep disruption actually precedes certain types of mental illness, and we've shown that in those young individuals who are at high risk of developing bipolar disorder, they already have a sleep abnormality prior to any clinical diagnosis of bipolar. The other bit of data was that sleep disruption may actually exacerbate, make worse, the mental illness state. My colleague Dan Freeman has used a range of agents which have stabilized sleep and reduced levels of paranoia in those individuals by 50 percent.
So what have we got? We've got, in these connections, some really exciting things. In terms of the neuroscience, by understanding these two systems, we're really beginning to understand how both sleep and mental illness are generated and regulated within the brain. The second area is that if we can use sleep and sleep disruption as an early warning signal, then we have the chance of going in. If we know these individuals are vulnerable, early intervention then becomes possible. And the third, which I think is the most exciting, is that we can think of the sleep centers within the brain as a new therapeutic target. Stabilize sleep in those individuals who are vulnerable, we can certainly make them healthier, but also alleviate some of the appalling symptoms of mental illness.
So let me just finish. What I started by saying is: Take sleep seriously. Our attitudes toward sleep are so very different from a pre-industrial age, when we were almost wrapped in a duvet. We used to understand intuitively the importance of sleep. And this isn't some sort of crystal-waving nonsense. This is a pragmatic response to good health. If you have good sleep, it increases your concentration, attention, decision-making, creativity, social skills, health. If you get sleep, it reduces your mood changes, your stress, your levels of anger, your impulsivity, and your tendency to drink and take drugs. And we finished by saying that an understanding of the neuroscience of sleep is really informing the way we think about some of the causes of mental illness, and indeed is providing us new ways to treat these incredibly debilitating conditions.
Jim Butcher, the fantasy writer, said, "Sleep is God. Go worship." And I can only recommend that you do the same.
Thank you for your attention.