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The Relationship Between Alzheimer’s Disease & Sleep

A few years ago I read a book called Why We Sleep by Matthew Walker, since then I have dramatically changed the way I approach my sleep as well as coach my clients.


I recommend this book to pretty much everyone, even they have no issues with sleep. Over the years whenever Dr Walker is on any podcasts I come accross I always take the timeout to listen, and so this week I came accross a podcast with Tim Ferriss and Matthew Walker. In the podcast Tim Ferriss asked Dr Walker about the relationship between Alzheimer's disease and sleep and here was the answer.

Alzheimer's disease is a form of dementia typified by memory decline and there are at least two protein pathological culprits that contribute to Alzheimer’s disease, one of those is called beta amyloid which is a sticky toxic protein that build up in the brain and the other is called tau protein.


How are these related to sleep?


This has unfolded in a three part story.


The three parts are correlation, causation and then mechanism. What was discovered early on was that individuals who reported to sleep for 6 hours or less accross their lifespan had a significant higher risk of developing high amounts of this toxic beta amyloid and tau protein in the brain.


Then it was discovered that two sleep disorders, insomnia and sleep apnea were associated with higher risk of both Alzheimer’s pathology but also the transition to early stages and ultimately the transition to full blown Alzheimer’s disease.


There was a recent meta analysis looking at 27 different studies and what they found is that people who had sleep problems during their lifespan were about 3.78 times more likely to develop the early stages of Alzheimer’s disease in a premature fashion.


These studies were simply correlational, they don’t prove causality, so correlation then went in search of causation and what was discovered accross species both in animals and in humans they found that if we deprive individuals one night of sleep or even just deprive them selectively of just their deep sleep across a single night then the next day an immediate and significant increase is seen in beta amyloid and tau protein circulating in the bloodstream and circulating in the cerebral spinal fluid of the brain which is this fluid that bathes the brain. Using PET scanning images they were able to see that same build up of amyloid within the brain itself.


There was a recent study that looked at these signals of metabolic waste in the brain and what they found is that just after one night of sleep deprivation even a full recovery night of sleep was not sufficient to downgrade those metabolic toxins that have been building up in the brain.


This is a demonstration that if we remove this thing called sleep, or even selectively excise different types of sleep we can manipulate the amount of Alzheimer’s protein in then brain the next day.


This is the causal evidence.


Causation then wanted a mechanism. So if this is the bad that happens if we take sleep away from us then what it is about sleep when we get it that deescalates our Alzheimer’s disease pathology risk?

This comes on to a series of discoveries by a wonderful scientist at the university of Rochester called Maiken Nedergaard and she made three stunning discoveries, the first thing that she discovered is that the brain has a cleansing system called glymphatic system, the second thing she discovered was, that cleansing system in the brain is not always switch on in high flow volume across the 24 hour period, instead it is particularly active when we fall asleep and when we go into deep sleep, it is during this sleep that the pulsing cleansing system kicks into high gear.


This was then the shift to find out what those things are that the brain is cleansing during deep sleep and this is what brings us back to Alzheimer’s disease. Two of the pieces of the metabolic byproduct that were being washed away by deep sleep were beta amyloid and tau protein, these two culprits associated with Alzheimer’s disease.


Wakefulness is low level brain damage and sleep is the sanitary salvation.


Now we can understand why night after night if you are not getting the sleep that you need, you are not cleansing the brain of the pathology.


It is important to realise that it's not as vast that if you miss one night of sleep the next day you guaranteed your Alzheimer's disease fate, but if night after night if you are not cleaning the brain it becomes like compounding interest on a loan, it continues to escalate time and time again, night after night.


If this is not depressing enough, scientists went on to make a further discovery that is a vicious cycle, that Alzheimer’s disease pathology, those proteins do not build up on the brain homogeneously, they don’t build up in all areas of the brain equally. The parts of the brain that start to get attacked by Alzheimer’s disease early on are unfortunately the same regions of the brain that generate deep sleep, the same stage of sleep that is connected with cleansing and so now we have this vicious circle that if you don’t get enough sleep each night you get more of that Alzheimer’s build up, the more that builds up the less the brain is capable of generating deep sleep, the less deep sleep the more that builds up.


The principle epicentre that generates deep sleep is a part of the frontal lobe in the brain, particularly the middle part of the frontal lobe, the prefrontal cortex and this is the part of the brain that Alzheimer’s attacks early on and it's the same region that is generating the deep sleep.


Recently in a podcast with Dr Huberman and Dr Gina Poe they talked about the importance on not just the duration and depth of our sleep but actually getting to sleep at relatively the same time each night ensures that we get adequate growth hormone release in the first hours of sleep, these first hours of sleep are also known as deep sleep which as we have seen above is hugely important to remove the waste from our brains.

Even if you get adequate time of sleep but you go to sleep two hours later than your typical bedtime on any given night you actually miss the window for growth hormone release as well the all important deep sleep.

Getting growth hormone in our sleep is absolutely critical to our immediate and long term health. As DR Poe explains there are critical brain circuits and hormones circuits that regulate not just the duration and depth, and quality and timing of sleep but when we place our bout of sleep, that is when we go to sleep each night, plus or minus about half hour strongly dictates whether or not we will experience all the health promoting benefits of sleep.


I find this astonishing as for so many years of my life I did not have regularity to my bed times, and I can almost guarantee that most of you reading this also don't have regular bedtime 7 days per week.


More and more it is becoming clear to me that Sleep is the NUMBER 1 pillar of health and we MUST take it very seriously.


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