The mystery of sleep - finally solved?

Wednesday 14 February 2018

I wrote a post a couple of months ago called the mystery of sleep where I cogitated on what I consider to be one of the great unknowns in both science and life in general: why do we spend a third of our lives sleeping?

Since then I read a very interesting book called "Why we sleep: the new science of sleep and dreams," by Matthew Walker, an enthusiastic, almost evangelical sleep scientist who is currently Professor of Neuroscience and Psychology at the University of California, Berkeley. Incidentally, he sports a thick, stylised blond fringe (think eighties boy band meets Donald Trump) which somehow makes it hard to take him completely seriously.

That said, his book is a good read, if a little repetitive in places and with some of his statistics (e.g. “200% reduction”) needing to be taken with a pinch of salt.

He postulates several reasons for sleep, backed up by various experiments, some of them pioneered by his own research team.

So how did my very naïve theories stack up against the Professor’s? 

I hypothesised that the purpose of REM sleep is memory formation, essentially copying new experiences captured by the hippocampus into permanent storage in the cortex (i.e. the grey matter). This process is correct, except that it happens in NREM sleep rather than REM sleep. Apparently NREM sleep has a number of other functions too, one of the most important of which is allowing the body to rest and repair itself. Lack of NREM sleep therefore has a significant impact on both memory formation (pulling an all-nighter before an exam is generally not a good idea) and general physical health (lack of sleep degrades the immune system for example, making us more likely to get ill).

What then is the purpose of REM sleep, and of dreaming? 

Professor Walker gives compelling evidence for two functions: one is creativity and the second is to do with processing emotions. 

Dreaming is, according to his theories, the result of REM sleep playing around with forming new connections in the cortex: trying to link past and recent experiences in new ways, building large associative networks of our learnings. And this leads to creativity. There are numerous examples of people who woke up with a genius idea after a good night’s sleep. For example, Mary Shelley famously dreamt the story of Frankenstein and Paul McCartney woke up one morning with the tune of “Yesterday” in his head. Andrew Wiles frequently “slept on it” during his eight-year odyssey to solve one of the most famous – and hardest - problems in mathematics, the 350-year-old Fermat’s Last Theorem. 

The second purpose of REM sleep is to help the brain separate memories from their related emotional responses (for example fear, processed by a structure called the amygdala). Dreaming therefore has a therapeutic effect on recent stresses.

Post-traumatic stress disorder happens when this mechanism doesn’t work: the person dreams the same event again and again but each time the brain fails to separate the emotional reaction from the memory. The net effect is a nightmare that repeats itself night after night.

His overall argument then, is that REM sleep has evolved in humans to give us superior intelligence coupled with control over our emotions. 

Broadly speaking, it seems my own theories were along the right lines but, as expected, I missed some nuances.   

Professor Walker’s book covers a lot of ground, so here are just a sample of other miscellaneous sleep facts from it that I found interesting:  

• About 8 hours per night is recommended for adults
• There is no such thing as a sleep bank that you can borrow from: if you miss a lot of sleep you can’t make up for it later
• Teenagers’ body clocks are shifted forward, so they simply can’t help staying up late and sleeping in
• The previous point has implications for the education system: schools that start later in the day achieve better exam results
• 18 degrees Celsius is the optimum temperature for sleeping
• The “two sleeps” pattern popular in Victorian times was a cultural thing rather than something innate – in general we are designed to sleep through the night
• Sleep deprivation kills many more drivers than drink driving

On the question of how to sleep better, he gives 12 tips for a good night’s sleep. These are mostly fairly obvious but still worth listing:     

1. Stick to the same routine at weekends
2. Exercise is good, but not just before bedtime
3. Avoid caffeine late in the day
4. Avoid alcohol before bed (in my view, this is the hardest one of all…)
5. Avoid large meals late at night
6. Avoid medicines that interfere with sleep
7. Don’t nap after 3pm
8. Allow some time for unwinding before bed
9. Have a hot bath before bed
10. Dark, cool and gadget-free bedroom
11. Get daylight exposure during the day
12. Don’t lie in bed awake; get up, do something then go back to bed when tired (in other words keep the association between bedroom and sleep)

Since finishing the book a couple of weeks ago, I resolved follow sleep hygiene more strictly, particularly avoiding screens in the bedroom, and trying to keep to the same routine at weekends as during the week.

I still have a way to go but I'm pleased to say that, as a result, the quality of my sleep is starting to improve.  Sleep deprivation and fatigue is currently the biggest problem I have with Parkinson's and I am starting to bring the under control at last.

Thanks to the work of Matthew Walker and others, we are now finally starting to understand the purpose of sleep. In the process, we are learning to appreciate how important it is, and how to overcome the modern-day culture of burning the candle at both ends, thereby reclaiming what nature intended with all its associated health benefits: a good night's slumber.

On that note, it's time for me to get away from this screen and enjoy the remainder of Valentine’s day before winding down for bed...