Sleep expert Matthew Walker breaks down the many effects of sleep deprivation on your brain and body. Following is a transcript of the video.
Matthew Walker: My name is Matthew Walker, I am a professor of neuroscience and psychology at the University of California, Berkeley, and I am the author of the book "Why We Sleep."
We certainly know that a lack of sleep will actually prevent your brain from being able to initially make new memories, so it's almost as though without sleep the memory inbox of the brain shuts down and you can't commit new experiences to memory. So those new incoming informational emails are just bounced, and you end up feeling as though you're amnesiac. You can't essentially make and create those new memories.
We also know that a lack of sleep will lead to an increased development of a toxic protein in the brain that is called beta amyloid and that is associated with Alzheimer's disease because it is during deep sleep at night when a sewage system within the brain actually kicks in to high gear and it starts to wash away this toxic protein, beta amyloid. So if you're not getting enough sleep each and every night, more of that Alzheimer's-related protein will build up. The more protein that builds up, the greater your risk of going on to develop dementia in later life.
What are the effects of sleep deprivation on the body? Well, there are many different effects. Firstly, we know that sleep deprivation affects the reproductive system. We know that men who are sleeping just five to six hours a night have a level of testosterone which is that of someone ten years their senior. So a lack of sleep will age you by almost a decade in terms of that aspect of virility and wellness.
We also know that a lack of sleep impacts your immune system. So after just one night of four to five hours of sleep, there is a 70% reduction in critical anticancer-fighting immune cells called natural killer cells. And that's the reason that we know that short sleep duration predicts your risk for developing numerous forms of cancer. And that list currently includes cancer of the bowel, cancer of the prostate, as well as cancer of the breast. In fact, the link between a lack of sleep and cancer is now so strong that recently the World Health Organization decided to classify any form of nighttime shift work as a probable carcinogen. So in other words, jobs that may induce cancer because of a disruption of your sleep rate rhythms.
We also know that a lack of sleep impacts your cardiovascular system because it is during deep sleep at night that you receive this most wonderful form of effectively blood pressure medication. Your heart rate drops, your blood pressure goes down. If you're not getting sufficient sleep, you're not getting that reboot of the cardiovascular system, so your blood pressure rises. You have, if you're getting six hours of sleep or less, a 200% increased risk of having a fatal heart attack or stroke in your lifetime.
There is a global experiment that is performed on 1.6 billion people twice a year and it's called daylight saving time. And we know that in the spring, when we lose one hour of sleep, we see a subsequent 24% increase in heart attacks the following day.
Another question, perhaps, is what is the recycle rate of a human being? How long can we actually last without sleep before we start to see declines in your brain function or even impairments within your body? And the answer seems to be about 16 hours of wakefulness. Once you get past 16 hours of being awake, that's when we start to see mental deterioration and physiological deterioration in the body. We know that after you've been awake for 19 or 20 hours, your mental capacity is so impaired that you would be as deficient as someone who was legally drunk behind the wheel of a car. So if you were to ask me what is the recycle rate of a human being, it does seem to be about 16 hours and we need about eight hours of sleep to repair the damage of wakefulness. Wakefulness essentially is low-level brain damage.
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