Sleep is your Super Power
Men who sleep five hours a night have significantly smaller testicles than those who sleep seven hours or more. In addition, men who routinely sleep just four to five hours a night will have a level of testosterone which is that of someone 10 years their senior.
So a lack of sleep will age a man by a decade in terms of that critical aspect of wellness. We see equivalent impairments in female reproductive health caused by a lack of sleep. I tell you about the wonderfully good things that happen when you get sleep, but the alarmingly bad things that happen when you don’t get enough, both for your brain and for your body.
Let me start with the brain and the functions of learning and memory, because what we’ve discovered over the past 10 or so years is that you need sleep after learning to essentially hit the save button on those new memories so that you don’t forget.
Recently, we discovered that you also need sleep before learning to prepare your brain, almost like a dry sponge ready to initially soak up new information.
Without sleep, the memory circuits of the brain essentially become waterlogged and you can’t absorb new memories.
In one study we decided to test the hypothesis that pulling the all-nighter was a good idea. So we took a group of individuals and we assigned them to one of two experimental groups: a sleep group and a sleep deprivation group. The sleep group got a full eight hours of slumber, but the deprivation group was kept awake in the laboratory, under full supervision. There’s no naps or caffeine, by the way, so it’s miserable for everyone involved.
The next day, those participants were placed inside an MRI scanner and they tried to learn a whole list of new facts while they were taking snapshots of brain activity.
When you put those two groups head to head, what you find is quite significant. A 40% deficit in the ability of the brain to make new memories without sleep.
I think this should be concerning, considering what we know is happening to sleep in our education populations right now. In fact, to put that in context, it would be the difference between a child acing an exam versus failing it miserably
We’ve gone on to discover what goes wrong within your brain to produce these types of learning disabilities. There’s a structure that sits on the left and the right side of your brain, called the hippocampus. You can think of the hippocampus almost like the informational inbox of your brain. It’s very good at receiving new memory files and then holding on to them. When you look at this structure in those people who’d had a full night of sleep, we saw lots of healthy learning-related activity.
Yet in those people who were sleep-deprived, we actually couldn’t find any significant signal whatsoever. So it’s almost as though sleep deprivation had shut down your memory inbox, and any new incoming files — they were just being bounced. You couldn’t effectively commit new experiences to memory.
Do you remember those folks that got a full eight hours of sleep? Well, we can ask a very different question: What is it about the physiological quality of your sleep when you do get it that restores and enhances your memory and learning ability each and every day?
By placing electrodes all over the head, what we’ve discovered is that there are big, powerful brain waves that happen during the very deepest stages of sleep that have riding on top of them these spectacular bursts of electrical activity that we call sleep spindles.
It’s the combined quality of these deep-sleep brain waves that acts like a file-transfer mechanism at night, shifting memories from a short-term vulnerable reservoir to a more permanent long-term storage site within the brain, and therefore protecting them, making them safe.
It is important that we understand what during sleep actually transacts these memory benefits, because there are real medical and societal implications. Let me just tell you about one area that we’ve moved this work out into, clinically, which is the context of aging and dementia.
Because it’s of course no secret that, as we get older, our learning and memory abilities begin to fade and decline. But what we’ve also discovered is that a physiological signature of aging is that your sleep gets worse, especially that deep quality of sleep that I was just discussing.
Only last year there was evidence published that these two things, they’re not simply co-occurring, they are significantly interrelated. It suggests that the disruption of deep sleep is an underappreciated factor that is contributing to cognitive decline or memory decline in aging, and most recently we’ve discovered, in Alzheimer’s disease as well.
Unlike many of the other factors that we know are associated with aging, for example changes in the physical structure of the brain, that’s fiendishly difficult to treat. We now understand that sleep is a missing piece in the puzzle of aging and Alzheimer’s. This is exciting because we may be able to do something about it.
One way that we are approaching this is not by using sleeping pills. Unfortunately, they are blunt instruments that do not produce naturalistic sleep.
Instead there is a method being created based on this. It’s called direct current brain stimulation. You insert a small amount of voltage into the brain, so small you typically don’t feel it, but it has a measurable impact.
If you apply this stimulation during sleep in young, healthy adults, as if you’re sort of singing in time with those deep-sleep brain waves, not only can you amplify the size of those deep-sleep brain waves, but we can almost double the amount of memory benefit that you get from sleep.
The question now is whether we can translate this same affordable, potentially portable piece of technology into older adults and those with dementia.
Can we restore back some healthy quality of deep sleep, and in doing so, can we salvage aspects of their learning and memory function? That is my real hope now. So that’s an example of sleep for your brain, but sleep is just as essential for your body.
We’ve already spoken about sleep loss and your reproductive system. I could tell you about sleep loss and your cardiovascular system, and that all it takes is one hour.
Because there is a global experiment performed on 1.6 billion people across 70 countries twice a year, and it’s called daylight saving time.
Now, in the spring, when we lose one hour of sleep, we see a subsequent 24% increase in heart attacks that following day. In the autumn, when we gain an hour of sleep, we see a 21% reduction in heart attacks. Isn’t that incredible?
We see exactly the same profile for car crashes, road traffic accidents, even suicide rates.
As we dive deeper, I want to focus on this: sleep loss and your immune system. We are going to discuss natural killer cells, and you can think of natural killer cells almost like the secret service agents of your immune system. They are very good at identifying dangerous, unwanted elements and eliminating them.
These cells are what fight off and destroy a cancerous tumor mass. So what you wish for is a virile set of these immune assassins at all times, and tragically, that’s what you don’t have if you’re not sleeping enough.
In one experiment, participants simply had their sleep restricted to four hours for one single night. Then the study took a look at the reduction in immune cells after just one night. The results were not minimal — it’s not 10%, it’s not 20%. There was a 70% drop in natural killer cell activity.
That’s a concerning state of immune deficiency, and you can perhaps understand why we’re now finding significant links between short sleep duration and your risk for the development of numerous forms of cancer.