Sleep is very important to the brain. It’s restorative, and it helps memory and thought processing. The following are notes from section 4 of Biohacking Your Brain’s Health – a course I took on Coursera.
Sleep and the Brain: Sleep Cycles
There are 5 stages of sleep. They are levels 1-4, and REM sleep. R.E.M. sleep is also called Paradoxical Sleep. Typically, it takes 90-110 minutes to go through a full sleep cycle.
The REM cycle gets longer as the night goes on, and a sleeper will mostly cycle from level 2, down to REM, and back up levels 4 and 3 to 2, and then back down to REM again.
Sleep studies use EEG and EKG machines to monitor brainwaves and heart and muscle activities. Oxygen levels are measured, and scientists now have a decent picture of what happens physically when we sleep.
The 5 Stages of Sleep
Level 1: drifting in and out, slow eye movement
Level 2: still eyes, slow brain activity, sleep spindles
Levels 3 & 4: these are so similar that I’m not sure why they’re different levels. In 3 & 4, it is slow-wave, deep sleep. This is when some people sleepwalk
R.E.M. or Paradoxical Sleep: this accounts for about 20% of our overall sleeping time. This stage is characterized by rapid eye movement, increased pulse and breathing, and sleep paralysis or paralyzed muscles.
Sleep patterns appear to change, and become increasing fragmented over time. Babies sleep a lot, and seniors do not. Seniors often have more fragmented, or shorter sleeping periods. Young adults have a lot of slow wave or level 3 or 4 sleep.
Biology of Sleep
Adenosine, norepinepherine, histamine, dopamine, setatonin, acetylcholine: neurotransmitters project from brainstem and forebrain to various parts of the cortex. These neurotransmitters fire off while awake, and then decrease and finally stop in REM sleep. In sleep, acetylcholine neurotransmitter levels rise very high, and this is what causes sleep paralysis.
During REM sleep, there’s reduced activity in the reasoning part of the brain, the frontal cortex. However, there’s activity in the anterior cingulate, the amygdala, the hypothalamus, and the basal forebrain, which are all part of emotional regulating and processing.
Wakefulness inhibits sleep and vice versa. It’s like a sea-saw. This is also called mutual inhibition. Wakefulness and sleep are interconnected and balancing drives.
The homeostatic sleep drive, and the circadian rhythm are regulated by hormones. As the day goes on, the homeostatic sleep drive increases. Cortisol levels decrease and melatonin levels increase. This triggers sleepiness.
Circadian Rhythm: Your Internal Wakefulness Clock
The circadian rhythm controls sleep patterns. Your eyes pass light and darkness information to a part of the brain called the supra-chiasmatic nucleus. The supra-chiasmatic nucleus synchronizes your sleeping pattern with external light and dark conditions.
Your circadian rhythm is your internal clock. Along with hormones like cortisol and melatonin, your metabolism, gene expression and physical activities also influence your natural internal rhythms.
The circadian clock, and cortisol production, slacken as the day wears on. In sleep melatonin production continues until just before you wake. This is when the homeostatic sleep drive winds down, and the circadian rhythm kicks your arousal drive into gear again.
What Happens During Sleep?
- WASTE MANAGEMENT: Your central nervous system flushes out toxins via the glymphatic system which is 60% more active during sleep. Throughout the day, harmful proteins like beta-amyloid along with other neuro-toxins accumulate. When you sleep, the glymphatic system flushes these toxins away from your brain and out of your central nervous system.
- MEMORY & LEARNING: your declarative or conscious memory, like something you memorize through repeated recitation, is encoded in the hippocampus. Your implicit or non-declarative memory, like knowing how to ride a bike, is stored in the cerebellum and basal ganglia. During slow wave and REM sleep stages, auditory, visual and motor learning, like from studying, merge and consolidate. Sleep deprivation, particularly slow wave and REM sleep deprivation, negatively impacts learning.
- HORMONES: hormones and sleep are interconnected. Hormones are set by sleep. A cortisol surge wakes you, but cortisol production is suppressed in sleep. HGH, or human growth hormone, increases in sleep, especially in slow wave sleep. Growth hormone helps with growth, and tissue repair. Thyroid hormones peak around midnight, and gradually decrease throughout the day
The Biggest Public Health Crisis You Never Heard About
Forget the coronavirus pandemic, sleep deprivation has to be one of the most massive public heath problems in the world. And nobody seems to care. There are no good stats for me to give you because the problems, deaths and diseases associated with sleep deprivation are under-reported. In fact, powering through the day on little sleep is often bragged about, like it’s a badge of honor.
Sleep deprivation causes a lot of daytime dysfunction. There’s the economic impact of lower productivity, and there’s also higher mortality and risk of injury. Any decent traffic cop could tell you, sleepy drivers are as dangerous as drunk drivers. And it doesn’t stop there: workplace accidents, diseases and so many other problems can tie back to a chronic lack of sleep.
Disease and Sleep Deprivation
If you’ve struggled to lose weight, getting the proper amount of quality sleep might be a big help to you. Just like your sleep and wakefulness drives, your fullness (leptin) and hunger (ghrelin) hormones operate in a sea-saw fashion.
Studies have measured what happens to these hormones when sleep deprived or extended. If a person gets about 4 hours of sleep, their fullness hormone, leptin, decreases in production by around 20%. This means a person doesn’t get the feeling of fullness. Simultaneously, as the leptin stalls, ghrelin and cortisol levels surge, giving a body the feeling of hunger. It’s easy to see how lack of sleep can lead to obesity.
Sleep deprivation might also play a role in diabetes heart disease, and depression. When lacking sleep, glucose levels rise despite similar insulin levels creating imbalances commonly seen in diabetics. Also there are increased inflammation markers which are linked to heart disease. Still worse, this inflammation does not go back to baseline right away, but can stay elevated for an extended period of time. These inflammation markers are also liked to depression.
Recall that the brain flushes out toxins when you sleep. Sleep deprivation is logically tied to cognitive impairment, brain tissue loss and accelerated brain aging.
Why Do People Lose Sleep?
- GO TO BED: the number one reason people don’t sleep enough is that they don’t go to bed.
- STRESS: around 65% of people report that they don’t sleep well because of stress. In turn, lack of sleep makes coping with stress more difficult and stressful.
- MENOPAUSE: hot flashes disturb healthy sleep
- CHRONIC PAIN: pain and sleep do not mix well.
- CHRONIC DIGESTIVE DISORDERS: digestive disorders, and heavy meals before bed disturbs your sleep
- CHRONIC INSOMNIA: trouble falling and staying asleep, difficulty getting back to sleep once awakened, or waking up too early
- SLEEP APNEA/OBSTRUCTIVE SLEEP APNEA: this is when a person stops breathing temporarily in the night. Micro arousals disturb sleep. This condition is linked to obesity, diabetes, hypertension, depression, heart disease and stroke
How to Get Better Sleep
Go to bed! Yes, this seems obvious, however not going to bed at a decent hour is the #1 reason people are sleep deprived. Our drive to succeed and be productive can sometimes push us to work into the wee hours, but beware. You will ultimately pay a cost somewhere in our life for short-changing yourself on sleep.
Use blue-light filters on your screen devices late at night because the harsh blue light mimics UV light in our brains and can keep us awake. Avoid bright artificial light 1-2 hours before bed, and turn off your phones, tablets TV or other screens 1 hour before bed.
Avoid eating anything heavy before bed. Also, keep in mind that alcohol disrupts your sleep cycles. No judgement, just please be aware that passing out is not sleeping, OK? Finally, avoid caffeine before bed.
Make your sleeping environment ideal for sleep. Keep the room dark and cool. Use blackout curtains and a small air conditioner or fan if you must. The ideal temperature for sleep is 18-20 degrees Celsius, or about 68 degrees Fahrenheit.
Using the bed only for sleeping or sex is also helpful because it conditions the mind that bed equals sleep. In contrast, if you read and watch TV in bed, you mind will not automatically associate bed and sleep.
For your health, please do anything you can to improve and protect your sleep. As I’ve hopefully explained, sleep deprivation is not cool, in fact, it’s dangerous.