I recently read “Why We Sleep” By Matthew Walker.  Forget your Stephen King novels, I can honestly say this is the scariest book I have ever read.

I’m not going to run through all the things you should or shouldn’t be doing; you probably know most of it already and I’ll bet you still don’t get a relaxing 8 hours a night. What I will say is that the research that Walker quotes on memory function and ability to problem solve when even mildly sleep deprived is the stuff of nightmares.


A few helpful facts:

Sleep is not just about resting.  It is a very active state and your brain is as busy during sleep as it is whilst awake. (Perhaps more so for some!)

You will have heard of REM sleep (Rapid Eye Movement) and nREM sleep (a catchy term meaning non-REM sleep.)  You may also know that dreaming occurs during the REM portion of sleep.

What is less widely known is the function of these two types of sleep.  nREM takes the days memories and transfers them from short to long-term memory.  It replays events and learnt facts over and over to embed them in to our minds.


REM Sleep

REM sleep has two main functions.  Firstly, we re-live the emotional moments of the day.  Importantly, as we do this there is no Cortisol (the stress hormone) in our brains.  This disassociates the event from the potentially painful emotions that went with it.  This effectively washes the stress away and allows us to desensitize ourselves, so that we don’t go in to panic mode and can deal more effectively with similar events when they next occur.

Secondly, REM sleep, deliberately throws together really disparate ideas, looking for patterns and helping us to make connections and to put things learnt in to context.  It thus helps us to understand things properly and to apply the learning to new situations.  It expands our ability to problem solve.


Late to bed, early to rise?

Sleep isn’t all uniform and it doesn’t just start from zero when we first fall asleep. We have a body clock (based in the suprachiasmatic nuclei) which tracks what time of day it is and the type of sleep we get varies at similar times of night.  Earlier on in the night (say 10pm-3am) we get far more nREM sleep and we get more REM sleep later on (say 3am-8am).  Actual timings will be different for all of us.

This is governed by our body clock and not by when we start sleeping.  If you go to bed at 3am, you may miss out on the vast majority of your nREM sleep (and not remember much of what you have learnt from the day before) If you get up at 4am then then you will miss out on most of your REM sleep and won’t make the connections you might have done and you won’t be able to apply things learnt the day before to other situations well. Your problem solving capacity will be impaired.

Further, it’s not just a one night thing.  A poor night’s sleep affects your memory retention and problem solving abilities from several days ago.

Oh and one more scary thing to end on.  Driving 16 hours after having last slept gives you the same reaction times as someone just over the legal alcohol limit.  Don’t underestimate the impact of going too long without sleep.

The message is pretty clear.  If you want to perform at close to your peak, get a decent night’s sleep (perform, sleep, repeat!)


Click on this link if you want to explore how to change a habit