The Science of Optimal Sleep Hygiene


In this article I'll be summarizing the book Why We Sleep: Unlocking the Power of Sleep and Dreams. It was written by Dr. Matthew Walker, PhD in neurophysiology and former professor of psychiatry at Harvard Medical School.

Dr. Walker is a prolific reasearcher who examines the impact of sleep on human brain function in healthy and disease populations. To date, he has published over 100 scientific research studies and has received funding from the National Science Foundation and the National Institutes of Health.

I highly recommend the book, which is full of insightful information about the evolutionary basis of sleep, how it works in humans and other animals, and why it is so vitally important to our health.

Why do we sleep?

There does not seem to be one major organ within the body, or process within the brain, that isn't optimally enhanced by sleep and detrimentally impaired when we don't get enough.

Evolution didn't make a blunder. We sleep for a litany of functions that service both our brains and bodies. Sleep enriches a variety of functions within the brain.

The health effects of sleep

Sleep is the single most effective thing we can do to reset our brain and body health each day — Mother Nature’s best effort yet at contra-death.
  • Drowsy driving, hundreds of thousands of traffic accidents and fatalities. One person dies in a traffic accident every  hour in the US due to a fatigue-related error. Vehicular accidents due to drowsy driving exceed those of alcohol and drugs combined.
  • In countries where sleep has declined, these risks have increased: decreased immune system, increased appetite, Alzheimers, blood sugar levels, and lower blood pressure.

The two factors regulating sleep

  • 24 hours circadian rhthym – Internal 24 hours clock communicates to your brain and every organ in your body. Determines when you want to be awake and sleep. Including preferences for eating and drinking, moods, body temperature, metabolic rate, and release of numerous hormones. Likelihood to break an olympic record, or timing of birth and deaths all linked to circadian rhythm.
  • Sleep pressure (adenosine) – x

Circadian rhythm

What happens when individuals are prevented from sensing the cues they normally have about night and day? This question has been answered by placing volunteers in an environment (caves or bunkers have sometimes been used) without external cues about time  During a five-day period of acclimation that included social interactions, meals at normal times, and temporal cues (radio, TV), the subjects arose and went to sleep at the usual times and maintained a 24-hour sleep-wake rhythm. After removing these cues, however, the subjects awakened later each day, and the cycle of sleep and wakefulness gradually lengthened to about 28 hours instead of the normal 24. When the volunteers were returned to a normal environment, the 24-hour cycle was rapidly restored. 111

Suprachiasmatic nucleus

Presumably, circadian clocks evolved to maintain appropriate periods of sleep and wakefulness in spite of the variable amount of daylight and darkness in different seasons and at different places on the planet. To synchronize physiological processes with the day-night cycle, the biological clock must detect decreases in light levels as night approaches.

The receptors that sense these light changes are, not surprisingly, in the outer nuclear layer of the retina and project to the suprachiasmatic nucleus (SCN) of the hypothalamus, the site of the circadian control of homeostatic functions generally.

The SCN also governs other functions that are synchronized with the sleep-wake cycle, including body temperature hormone secretion, urine production, and changes in blood pressure. 111

Sleep and wake triggers (zeitgeibers)

Any signal that the brain uses for the purpose of clock resetting is termed a zeitgeiber.

The clock is called the suprachiasmatic nucleus.

  • Light is the primary zeitgeiber.  - governs body temp. wakefulness/sleep  irrespectice of id youre awake or not  
  • rhythms are different. chronotype. genetics. Greater ill health for "owls" because society isn't structured for them.

How does jet lag work?

Suprachiasmatic nucleus adjusts by 1 hour each day. So if you fly from the east coast to london (5 hours ahead) it will take you 5 days to get used to it.

  • Harder eastward - requires you to fall asleep earlier. Hard to will into action.
  • Westward, stay up later. Easier conscious prospect.

When shut off from outside influences our natural biological clock is slightly longer than 24 hours. Roughly 24 hours and 15 minutes. Westward travel is a longer 24 hour day, eastward is less.

Scientists have studies airplane cabin crews that fly long routes and rarely have a chance to recover. 1) parts of their brain related to learning and memory had physically shrunk, suggesting damage to brain cells. 2) short term memory significantly impaired. More forgetful of similar age and background.

How to use melatonin

Melatonin is released at night from the pineal gland. Has little influence on the generation of sleep itself. Melatonin is more like the official that shoots the starting pistol at a race. At dawn, light puts a brake pedal on the release of melatonin.

Melatonin synthesis increases as light decreases and reaches it maximal level between 2:00 and 4:00 a.m. In the elderly, the pineal gland calcifies and less melatonin is produced, perhaps explaining why older people sleep fewer hours and are more often afflicted with insomnia. 111

Can be helpful for jetlag. Melatonin isn't released at the new time zone (it's back on your old time zone). First, make sure you're using a legitimate compound.

7-8PM london time, triggers a rise in melatonin. Starts the timing signal. May still be difficult to fall asleep, but help.

Sleep stages

A healthy night’s sleep lasts about eight hours, and is divided between REM (rapid-eye movement) sleep, in which the brain is as active as it is when its owner is awake, and NREM (non-REM) sleep, a deeper sleep state that predominates in the first half of the night. Both of these states (and there are further sub-states within NREM sleep) serve a multitude of purposes. NREM sleep, for example, is crucial to memory retention, and to acquiring and refining our motor skills. REM sleep plays a role in our abilities to overcome negative feelings, read other people’s emotions and solve problems.

Glymphatic system

Wakefulness is low-level brain damage while sleep is neurological sanitation.

The purifying work of the glympathic system is accomplished by cerebrospinal fluid (CSF) that bathes the brain. The glial cells of the brain were shrinking by up to 60% during NREM sleep, enlarging the space around the neurons, allowing the CSF to clean out the metabolic refuse left by the day's neural activity.

Imagine the buildings of a large city physically shrinking at night, allowing crews easy access to pick up garbage, followed by a power wash treatment of every nook and cranny.

Amyloid protein and tau are cleaned.

Alzheimer's disease

Getting too little sleep will significantly raise your risk of developing Alzheimer's disease.

Dr. Walker notes that it's curious that Ronald Reagan and Margaret Thatcher, both very vocal and proud of sleeping only 4-5 hours a night, both went on to develop the disease.

Optimal sleep routine

Among these lists of activities to do and also avoid, there is common theme of coordinating your daily activities in line with the two sleep drives. They also heavily rely on zeitgeibers (sleep/wake resetters) to keep your sleep rhythms in line

A common theme is to avoid food, light, and movement in the evening – the same things you're trying to do in the morning (the zeitgeibers) that signal your body to wake up.

Do these activities

  • Consistent sleep and wake times – Establish a regular bedtime and wake-up time, even on weekends. It's hard for the body to adapt to weekend/monday morning shifts.
  • Get daytime sunlight – daylight exposure key to regulating sleep patterns. sunlight 30 min each day. Use bright lights in morning. Turn down lights before bed
  • Exercise – but not within 2-3 hours before bed. Any hard exercise session needs to be completed 3 hours before bedtime. So if you want to go to the gym at 7pm but you want to go to bed by 9pm, you may want to adjust that.
  • Make your bedroom cozy – Studies have been shown that when we are in an unfamiliar environment our brain is half awake. Make your bedroom cozy with familiar items, even if it’s your favorite comfort blanket or teddy bear. Think about it - we give those items to children because we know it makes them more comfortable. Subconsciously our brain still needs that. Sleep associations - Blankets, sentimental objects, and specific scents can help trigger the body into a sleepy state.
  • Lower your body temperature – Sleep is triggered by a drop in body temperature. Take a hot bath or a sauna which will draw blood to the skin and cool your core body temperature.
  • Relax before bed – schedule unwinding. reading/listening to music. Great time to turn the lights down low.
  • Nasal decongestion – It's common to have congested sinuses when you lie down at night which unfortunately can affect your sleep. There are a variety of non-medicated options available to improve this.
  • Supplements – CBD oil, valerian root, and melatonin.
  • Air quality – I have noticed correlation to air quality and my sleep. Granted I have sensitivity to smoke, but these disturbed my sleep which I could
  • Optimize sleep environment – The best conditions for sleep are dark, cool, and gadget free. Any light, especially blue light, is interpreted by your brain as daylight and can therefore suppress melatonin production at night. Black-out blinds or eye masks can help with this. Ear plugs can be used to prevent noise. Turn down the thermostat and get rid of anything that might distract you from sleep. Learn to sleep with a mask and ear plugs – I'm a very light sleeper and I never thought I'd be using these every night. There is an adjustment period but it's worth getting through it. One perk is now you can sleep on planes or while traveling.

Avoid these activities

  • Avoid caffeine and nicotine – can take 8 hours to wear off
  • Avoid alcohol – robs you of REM sleep. can impair breathing at night.
  • Avoid food – Whenever you eat something you trigger a release of hormones and kick your digestive system into action. This cycle can keep you awake at night and therefore you should not be eating several hours before bed. Avoiding food before bed can also prevent indigestion and urination. Also avoid large drinks.
  • Don't take naps after 3pm – can help make up for lost sleep, late afternoon naps make it harder to sleep
  • Down lie in bed awake – awake after 20 min, get up and do some relaxing activity until you feel sleepy. anxiety can make it harder to fall asleep.
  • Avoid blue light and bright light – Blue light (and bright light) suppresses melatonin production, the hormone that helps controls your circadian rhythm. You should be blocking blue light from your phone and avoiding bright lights at least 1-2 hours before bed. If you have an iPhone make sure to turn on Night Shift.

Final thoughts

We should be lobbying doctors to prescribe sleep, not sleeping pills.

Set an alarm 2 hours before bed. Do I always follow it? No, but it's a nice reminder and I do stay on top of it most nights. Following these tipds I've been sleeping better lately than I ever have in my life


Light / circadian rhythm

Low sleep effects