Why do we sleep?

Back in July 2019, I recommended a video by Dr. Matthew Walker about sleep.  He is director of the Center for Human Sleep Science at Berkley, and is regarded as one of the leading authorities on sleep in the world.  In 2018 he published the book Why We Sleep, which articulates much of what science understands about sleep.  Which isn't as much as we want to know, and much of what we do know has only been discovered in the past few years.

So I bought the book, and am now reading it.  I'm reading it now, because insomnia has risen to a crisis point, and I was wondering what insights it might bring.  At this point, I have a few takeaways. 

In case we didn't get it already, Dr. Walker emphasizes throughout the book the importance of sleep.  He also says that older people need just as much sleep as younger people, focused on the traditional 8 hours.

But older people have a lot more trouble sleeping.  This is not because they need less sleep, it's because even normal aging causes atrophy of the brain.  One particular part (located in the frontal area) that is particularly important to sleep is a casualty of atrophy.  But in Alzheimer's disease, this part of the brain is damaged earlier and more thoroughly than in normal aging.  So people with Alzheimer's disease suffer profound damage to their sleep.  If you speak with people working in memory care facilities you know that many of their residents will be up all night, at least without a sleep aid.  We should also recall that poor sleep aggravates Alzheimer's disease, resulting in a vicious cycle. 

The most commonly prescribed sleep aid for the elderly is trazadone.  Trazadone is not a hypnotic like Ambien, but is a low dose of an anti-depressant.  

The chemical that actually causes sleep is called adenosine.  It builds up in the brain while you are awake, but is degraded and removed from the brain while you are sleeping.  The steady build-up during wakefulness creates "sleep pressure" which is only relieved by sleep.  Sleep pressure is behind the sense of sleepiness you feel toward bed time.  (Caffeine blocks the adenosine receptors in the brain.) 

But it's more complicated than that.  Beside this cycle driven by buildup and exhaustion of adenosine, there is your circadian rhythm.  This is another cycle of alertness, one that may vary between people who are "morning people" (like me) and those who are not.  The hope is that the two cycles -- adenosine and circadian rhythm -- will align, because both promote sleep and alertness.  When the don't align (as in jet lag), you will have problems.

Another chemical associated with sleep is melatonin.  Some people treat melatonin supplements as a sleep aid, but it is not.  Both Dr. Walker and my sleep doctor say that when it seems to work, it is only acting as a placebo.  But that doesn't mean that it's not important to sleep.  And Dr. Walker cautions not to underestimate its power as a placebo.  (I have used melatonin off and on for a long time, but have never experienced a change in my sleep from either starting it or stopping it.)

The generation of melatonin is promoted by fading sunlight.  It then acts as a signaling mechanism to the body to say that it is now night.  This may, or may not, promote adenosine's action to cause sleep.    This is one reason why the adenosine cycle and circadian rhythm must be kept in sync for good sleep.

Dr. Walker likens melatonin to the race official firing the starting gun at the Olympic 100 meter race.  It declares the start of the race, but it's up to the runners to actually run the race.  

Dr. Walker also noted that it takes the body a day to adjust to one hour of jet lag.  So after traveling from the west coast to the east coast, it takes three days to adjust and align your rhythms.  But here, melatonin supplements have something to offer.  He says that a jet lagged person should take a melatonin supplement at about 7 or 8 p.m. to shock the body into realization that the sun has actually gone down.  This helps speed the adjustment.  In Dr. Walker's case, London, England is home, but he works and lives in California.  So he makes that trip regularly and must deal with 8 hours of jet lag each time -- and each way.  So he knows whereof he speaks.

For the moment, I am using trazadone to help me sleep.  It aggravates my balance and dizziness problems (when standing or walking), but I am at least feeling much more rested throughout the day.