【文章內(nèi)容簡介】 worse, much worse. They need nine hours for full brain performance, and many of them, on a school night, are only getting five hours of sleep. Itamp。39。s simply not enough. If we think about other sectors of society, the aged, if you are aged, then your ability to sleep in a single block is somewhat disrupted, and many sleep, again, less than five hours a night. Shift work. Shift work is extraordinary, perhaps 20 percent of the working population, and the body clock does not shift to the demands of working at night. Itamp。39。s locked onto the same lightdark cycle as the rest of us. So when the poor old shift worker is going home to try and sleep during the day, desperately tired, the body clock is saying, amp。quot。Wake up. This is the time to be awake.amp。quot。 So the quality of sleep that you get as a night shift worker is usually very poor, again in that sort of fivehour region. And then, of course, tens of millions of people suffer from jet lag. So who here has jet lag? Well, my goodness gracious. Well, thank you very much indeed for not falling asleep, because thatamp。39。s what your brain is craving.
　　One of the things that the brain does is indulge in microsleeps, this involuntary falling asleep, and you have essentially no control over it. Now, microsleeps can be sort of somewhat embarrassing, but they can also be deadly. Itamp。39。s been estimated that 31 percent of drivers will fall asleep at the wheel at least once in their life, and in the ., 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. Itamp。39。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.
　　So when youamp。39。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, itamp。39。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 youamp。39。re a really naughty tired brain, nicotine. And of course, youamp。39。re fueling the waking state with these stimulants, and then of course it gets to 11 oamp。39。clock at night, and the brain says to itself, amp。quot。Ah, well actually, I need to be asleep fairly shortly. What do we do about that when Iamp。39。m feeling pletely wired?amp。quot。 Well, of course, you then resort to alcohol. Now alcohol, shortterm, 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 doesnamp。39。t provide sleep, a biological mimic for sleep. It sedates you. So it actually harms some of the neural proccessing thatamp。39。s going on during memory consolidation and memory recall. So itamp。39。s a shortterm acute measure, but for goodness sake, donamp。39。t bee 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. Whatamp。39。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, amp。quot。I need carbohydrates,amp。quot。 and what it does is seek out carbohydrates and particularly sugars. So thereamp。39。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 youamp。39。re acutely stressed, not a great problem, but