Sleep Questions

The siesta is near-universal among non-industrial cultures. It is undoubtedly biological in basis.

Humans sleep an average of eight hours. All other primates sleep 10-15 hours. Our sleep is 25% REM sleep. Theirs is only 9%.

In the last two weeks of pregnancy the fetus experiences 12 hours of REM sleep, the most the individual will ever experience. It is also, not coincidentally, the time when the brain creates the most synaptic connections, which will be slowly whittled away for the remainder of its life.

There are as you know five distinct phases of sleep, REM sleep and four layers of non-REM sleep.

REM sleep, where we dream, is not the deepest. In fact it's the shallowest, occurring just after a period of NREM sleep as we're in the process of climbing back to consciousness. This is why it almost always seems like we just woke up from a dream when we wake up.

Newborns and fetuses dream a lot, and make synaptic connections as they're doing it. Could REM sleep play the same role in adults?

Yes, it turns out research shows we do.  After learning a difficult task, or trying to learn a difficult task, we'll often dream about it. During that dreaming our brains are forming new synaptic connections, often replaying the task we're trying to learn.  Research has shown musicians can play a new piece better after 8 hours of sleep. Athletes can perform new skills after "sleeping on them."  Computer programmers and mathematicians and authors can solve puzzles in their sleep.

And NREM sleep is equally useful for FORGETTING things we don't need to remember.  There are long brainwaves during NREM, distinct from the short waves of waking or dreaming. These waves travel between the hippocampus, where short term memories are stored, and the prefrontal cortex, where decisions are made, and the cortex, where permanent memories are stored.  Daily memories are brought to the prefrontal cortex and analyzed, and if found important, shuttled off to the cortex. Studies have shown that interrupting NREM sleep causes a person to remember more details of the day before.  Details that may not be useful, or optimal for efficient thinking.

And fetal dreaming? In adults there's a tiny part of the brain that immobilizes us during dreaming, so we don't thrash around or sleepwalk. That part of the brain doesn't begin to develop until just before birth. That's why mothers feel kicking.

And autistic people have a lot less REM sleep than the rest of us. It might be a cause, or a symptom, or just a correlation, nobody's quite sure.

Not only the autistic, but Alzheimer's patients commonly have sleep disorders.  The amyloid plaques that are symptomatic of Alzheimer's accumulate in the prefrontal cortex, the part of the brain that controls sleep patterns.

Is the correlation causative, or coincidental?  Nobody quite knows.

Margaret Thatcher and Ronald Reagan both boasted of sleeping only a few hours per night, and both developed Alzheimer's.

In order to fall asleep and sleep well, your body's core temperature needs to fall from 98.6° to somewhere around 96° or 95°. This triggers the suprachiasmatic nucleus to manufacture melatonin which regulates sleepfulness.

For YEARS I slept under electric blankets, or on top of an electric bed topper, or with an electric body pillow (or all three). I have slowly, over the past 40 years, stopped using all of these; these days I use nothing electric and climb into a cold bed, often with my arms outside the covers.

Now I know why.

This also explains why I like a cup of cocoa in the morning to wake up.

In the end, the sleep book turned out to be an odd mix. The best part, the part I was looking for, was the science of sleep: why we sleep, what happens when we sleep, what happens when we don't sleep.

Mixed in with that was some advocacy though. Pleas for later school start times so students could learn better. For an end to long shifts during medical residencies so budding doctors could learn easier and make fewer mistakes. Proposals for pilots and prisoners and law enforcement and the working world in general that sleep should be higher valued as necessary to peak job performance.

And speculative but compelling evidence that sleep disorders lead to Alzheimer's, dementia, delirium tremens, immune system disorders, ADHD, even cancer.

A plea for countries to stop using sleep deprivation as an interrogation technique, defining it as a form of torture.

And finally, a whole chapter on how to obtain your best sleep, i.e. a 'how to' chapter. Cool room, no food after six, no electronics, no blue lights, take a warm bath before retiring, always keep the same schedule.

Doesn't say anything about having kids or dogs in the house....