Sleep revisited


“To sleep, perchance to dream…”

So, did you sleep in over the long weekend? Chances are, you did. And maybe, if you’re like me, you felt guilty about it. After all, the summer’s almost over. We should all be outside enjoying the beautiful weather, or painting the house, or exercising, or spending time with our families, or doing anything other than wasting time sleeping.

But is sleeping really a waste of time? Scientists don’t think so. In fact, sleep is such a worthwhile way to spend time that every bird, fish, reptile and mammal does it. It’s so worthwhile that we spend a third of our lives doing it. And if that doesn’t make it seem worthwhile enough, if we don’t do it, we die.

Sleep researcher have learned a lot about sleep over the years by using electroencephalographs, which measure the brain’s electrical activity. When it is calm and relaxed, the brain produces regular electrical signals called alpha waves, seven to 12 times per second. We go through this stage as a precursor to sleep.

Next comes a stage of light sleep, during which we produce theta waves, at only three to seven cycles per second, with a low amplitude. These are interrupted by frequent bursts of activity called sleep spindles, at 12 to 15 cycles per second.

Next comes a period of regular, high-amplitude delta waves at only one to two cycles per second, with a few sleep spindles. Finally sleep deepens to the point that the brain produces wave patterns similar to those occurring in a coma, at one to three cycles per second.

And then the brain suddenly erupts with activity, similar to the waking state. Our eyes move rapidly under our closed eyelids, our heart rate, breathing rate and blood pressure, which dropped with our body temperature as we fell asleep, all go up, and we dream. (Fortunately our body remains effectively paralyzed. Otherwise we might act out our dreams, which could be embarrassing, if not downright dangerous.)

This stage is known as rapid-eye movement (REM) sleep, and lasts from 10 minutes to half an hour, generally lengthening as the night progresses. All these stages occur in a regular 90-minute cycle, usually four to six times a night.

How much sleep we need varies from person to person, and with age. A newborn sleeps up to 16 hours a day and a one-year-old around 13. Older children need less. Pre-pubescent children naturally tend to go to sleep and wake up earlier in the day, but research indicates that adolescent bodies are programmed to go to sleep later and wake up later–which is one reason teenagers like to stay up late and sleep in. But although teenagers won’t admit it, they still need more sleep than adults: about 9 1/2 hours. Adults generally need around eight hours.

Nobody knows why we sleep. A new hypothesis currently being tested suggests we sleep to replenish glycogen, the fuel that powers brain activity, and the brain has to be taken “off-line” for this replenishment because otherwise it would interfere with brain activity.

We don’t know why we dream, either. Is it vital to our well-being or just an interesting side-effect of brain chemistry?

We do know a little bit about what our dreams have in common, though. Research indicates, for example, that 75 percent of dreams are in color and two thirds include sound, but only about one percent include touch, taste or smell. Men most often dream about men; women dream about men and women equally. Women’s dreams are typically more emotional and have fewer people in them, though they tend to include more social interaction and more clothes: men tend to dream about money, weapons and nudity. (No wisecracks from the Freudians, please.) We dream about 90 minutes every night, but we usually only remember a dream every four or five days.

Even one night without enough sleep is enough to dull our mind; two nights, and the effects become more serious. In our 24-hour society, very few people get enough sleep…with occasionally catastrophic results. Nobody knows how many automobile, airplane and train crashes have been caused by people dozing off, or how many poor decisions have been made in emergency rooms–or board rooms or cabinet rooms, for that matter.

So if you slept in over the weekend, don’t berate yourself for being a lazy bum. You helped make the world a better, safer place.

And since I’m writing this late at night, I think it’s about time I went and did the same.

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