I recently spoke with a mid-level executive who told me they fall asleep on their laptop every night, usually around midnight. They then get up to conduct the day’s business starting around 5:00 AM. By any measure, this is chronic short sleeping. It made me wonder, what has gone so wrong with our understanding of the importance of a good night’s sleep?
I’m reading (not coincidentally) Dr Matthew Walker’s book “Why We Sleep.” I came across Matt’s work after listening to a conversation between Jocko Willink and Dr Kirk (Doc) Parsley, another sleep specialist, although from a different background to that of Dr Walker.
Matt Walker’s book is an eye-opener. I wish I had read it ten years ago. I wish I had known more about the importance of sleep twenty years ago. Walker comprehensively lays out the various biological processes that rely on sleep and how extremely detrimental chronic short sleep is on the body and the mind.
In my coaching practice, one of the conversations I have at the beginning of engagements is asking how my new coachee is sleeping. Having read Matt Walker’s book and listened to him on the Tim Ferriss podcast, I now have a decent neuro-biological reason for zooming in on that topic.
Most of us know the feeling of brain fog that settles in the day after a night of broken sleep. In Walker’s research and that of other neuroscientists, it becomes clear that this cognitive deficit is not imaginary. The ability to function rationally declines additively over nights of serial short sleep. In this case, short sleep is anything less than 7-8 hours per night. With just 7 hours per night, after ten nights, you are as negatively impacted as if you had stayed up for 24 hours straight. In other words, by the eleventh day, you are as cognitively impaired as if you have drunk enough alcohol to exceed the legal driving limit in most Western countries.
Sleep is a protective mechanism against the byproducts of neurological activity in the brain. These byproducts include tao and beta-amyloid proteins implicated in Alzheimer’s disease and dementia. Every night, in non-REM (Rapid Eye Movement) sleep, the brain runs a clean-up process called the glymphatic cycle to clean out the detritus. Studies have shown that just one (!) night of limited or broken sleep increases these proteins in the brain.
On a more fundamental level, sleep enables us to transfer memories successfully from the hippocampus to long-term memory structures in the brain. Numerous elegant studies referenced in the book show the impact on retention of learning from losing just a couple of hours of sleep per night. And the loss is immediate, and you can’t make it up after by “catch-up sleeping”. So if you don’t sleep after learning new information, you are very unlikely to be able to retain it efficiently.
From the point of view of our interactions with others, we are far more likely to be emotionally reactive due to lack of sleep. Our ability to regulate our emotions declines significantly; we’ve all experienced being grumpy due to lack of sleep. In addition, we’re more likely to gain weight because the hormones that regulate appetite (leptin and ghrelin) are also messed up. Consequently, research has shown we’re attracted to foods high in fat, salt and carbohydrates and that we eat more of them (typically 300+ calories more than on a day following a good sleep).
If the above wasn’t enough, lack of sleep has been shown to increase the inflammatory response in the body – the day after a night of limited or no sleep, we tend to run on cortisol. This has been shown to increase the risk of certain cancers over time – the International Agency for Research on Cancer has labelled night shift work as “probably carcinogenic”. Short sleep also negatively impacts the gut biome leading to higher rates of depression and various digestive disorders. A lack of sleep has also been shown to increase the risk of heart attack and strokes.
As someone who serially short-changed my sleep cycle at various points in my life (sometimes unavoidably due to having children, sometimes by choice because of work or leisure), I am genuinely wondering how much of the physical damage I carry around is a result of poor sleep practices.
This year, I’ve made a determined effort to correct that in my life, and I prioritise being in bed for at least 7.5 hours per night. I usually don’t sleep that long, but it’s better than the 5.5 hours I often got in the past. I don’t know how much of an impact this change will have, but having read Matthew Walker’s book and listened to him, Andrew Huberman, Doc Parsley and others discuss sleep from a scientific perspective, I believe it will be a very positive one. I strongly recommend you take the time to sleep because it might save or extend your life and health span. And read Matt’s book – it will hopefully change your mind about sleep.