Why We Sleep by Matthew Walker

Reading time: 18 minutes

Why an article about Sleep?

We, humans, spend eight hours daily (one-third of our life) sleeping; it is the single biggest investment of our time. For such a significant investment of our time, our understanding of sleep and its benefits is appalling.

This article, part of my Personal Growth Framework series, focuses on bridging the gap in our knowledge of sleep.

***

Sleep is the daily maintenance job that makes us healthy, wealthy, and wise. It enables us to learn, remember, and be creative.

From personal experience, I know how refreshed I feel after a good night’s sleep. I also know how difficult and tiresome a day can be to get through when we haven’t had adequate sleep. I am sure that’s been your experience too.

Yet sleep is increasingly neglected in our society. Not only is sleep being neglected, but society is also evolving in a way that could potentially penalize people who value their sleep.

Consequences being every major disease – Alzheimer’s, cancer, obesity, diabetes – has causal links to inadequate sleep.

How serious is the ‘sleep’ problem?

Two-thirds of adults throughout all developed nations fail to get the recommended eight hours of nightly sleep.
Routinely sleeping less than six or seven hours a night wrecks your immune system, more than doubling your risk of cancer.
Inadequate sleep – even moderate reductions for just one week – disrupts blood sugar levels profoundly, enough for you to be classified as pre-diabetic.
Insufficient sleep is a crucial lifestyle factor determining whether or not you will develop Alzheimer’s disease.
More than 50 percent of all children with an ADHD diagnosis have a sleep disorder, yet a small fraction knows of their sleep condition and its ramifications.

How often does a doctor ask his patient about the duration and quality of sleep while investigating or diagnosing these ailments?

What is the probability that you or your loved ones are taking medications for something that could be easily solved by sleeping for eight hours daily?

Given we invest one-third of our life sleeping, I have been searching for a book that explains the science of sleep and provides a guide of the do’s and don’ts based on its implications on our health and life. And I found an amazing book.

This article is based on the fascinating book Why We Sleep by Matthew Walker.

***

Why We Sleep by Matthew Walker – Book Review

In a first of its kind book written by a scientific expert, Professor Matthew Walker explores twenty years of cutting-edge research to solve the mystery of why sleep matters.

In this book, Matthew Walker, using layman’s language with limited medical jargon, systematically demolishes several myths and misconceptions about sleep. You don’t need prior medical or scientific knowledge to understand the topics covered in the book.

This book has been an eye-opener for me. I have already made some corrections in my life after reading this book and I intend to make a few more changes.

I strongly recommend everyone reading this article to buy and read this book. It will take a negligible investment of money and a nominal investment of your time. In return I promise you will gain an understanding the ‘how’ and the ‘why’ about your sleep, the biggest investment of time in your life. And Time is wealth.

After reading this book, I paid my customary visit to Goodreads to read some of the reviews of this book. To my surprise, the first review, and a fairly detailed one, was written by Bill Gates himself. He had been there two-three years ahead of me. No wonder one of us is a billionaire!

This review and the summary below is not a substitute for reading the entire book. So I repeat again, please buy the book and read it in detail.

***

Why We Sleep – Book Summary

The rest of the article summarizes the key highlights and takeaways from this book. Given the volume of takeaways from this book, I am splitting the summary into two parts.

Part 1 below covers about understanding sleep better.

Part 2 covers the health effects of sleep deprivation and dreaming.

Hope you find it useful.

Let’s get started by understanding a bit about the different aspects of our body involved in sleep.

Circadian Rhythm

We, humans, are solar-powered creatures.

Daylight is the most reliable, repeating signal that we have in our environment.

Every living creature on the planet with a life span of more than several days follows a natural cycle called the circadian rhythm.
Living organisms likely adopted a circadian rhythm to synchronize their activities, both internal (e.g., temperature) and external (e.g., feeding), with the daily orbital mechanics of Earth spinning on its axis, resulting in regular phases of light (sun-facing) and dark (sun hiding).
The average duration of a human adult’s circadian clock runs around twenty-four hours and fifteen minutes in length.
The light of the sun methodically resets the internal body clock every day to precisely twenty-four hours.

Suprachiasmatic Nucleus – The Biological Clock

There is a twenty-four-hour biological clock sitting in the middle of your brain is called the suprachiasmatic nucleus.

The suprachiasmatic nucleus is made up of 20,000 neurons (brain cells). It uses the daylight information to reset our body clock’s accuracy to a twenty-four-hour cycle.

Circadian Rhythm Controls Wakefulness and Sleep

Your biological circadian rhythm coordinates a drop in core body temperature as it gets dark, and it reaches its lowest two hours after sleep onset.

This temperature drop helps initiate sleep.
The circadian rhythm varies by person
- Larks or Morning types – have their peak wakefulness early in the day and also feel sleepy earlier. They make up 40% of the population.
- Owls or Evening types – Prefer going to bed late and waking up late. Approx. 30% of the population.
- Remaining 30% lie somewhere between the Larks and Owls.
An adult’s owlness or larkness, also known as their chronotype, is strongly influenced by genetics. It is part of the DNA hardwiring and is not a choice. It most likely had an evolutionary benefit (ensuring enough wakeful members in the tribe at any given time to guard against predators) during the early stages of humans as species.

Melatonin, Adenosine and Sleep Pressure

Your suprachiasmatic nucleus communicates its repeating night and day signal to your brain and body using a circulating messenger called melatonin.

Melatonin signals darkness to the entire body. It rises after dusk, released into the bloodstream from the pineal gland situated deep at the back of the brain. It provides official instruction to commence the event of sleep. It, however, does not participate in sleep itself.
Every moment you are awake, a chemical called adenosine is building up in your brain. This concentration of adenosine creates an increasing desire to sleep, known as sleep pressure.
High concentrations of adenosine turn down the ‘volume’ of wake-promoting regions in the brain and turn up the dial on sleep-inducing areas. It happens after twelve to sixteen hours of being awake.
The combination of abundant adenosine (high sleep pressure) and declining circadian rhythm (lowered activity levels) triggers a strong desire for sleep.
During a healthy eight hours of sleep, the brain degrades and removes the day’s accumulated adenosine. Without adequate sleep, the adenosine concentrations in the brain remain too high. This results in a feeling of chronic fatigue and reflects in many forms of mental and physical ailments.

What Happens During Sleep?

Senses and Perception of Time

Sleeping organisms adopt a stereotypical position (horizontal), have a lowered muscle tone, and show no overt displays of communication or responsivity.
There is a loss of external awareness – you stop perceiving the outside world and are no longer conscious of your surroundings.
Sensory signals still flood to your brain but are blocked by a perceptual barricade set up in a structure called the thalamus, which prevents them from going to the cortex (head office of your brain).
There is a feeling of a time cavity that, after waking up, makes you confident you’ve been asleep.
In dreams, you continue to have a sense of time, but dream time feels stretched out (time dilation).

Sleep Patterns and Brain Hemispheres

Brain Hemispheres

Dolphins and whales can sleep unihemispheric – meaning they will sleep with half a brain at a time! The other half must always stay awake to maintain life-necessary movement in the aquatic environment.
Studies suggest humans have a mild version of unihemispheric sleep. If you bring that person into a sleep laboratory or take them to a hotel – both of which are unfamiliar sleep environments – one half of the brain sleeps a little lighter than the other as if it’s standing guard.

Sleep Patterns – Monophasic and Biphasic

Most adults currently sleep in a monophasic pattern – that is, we take a long, single bout of sleep at night.
Tribes, whose way of life has changed little over the past thousands of years, sleep in a biphasic pattern – a longer sleep period at night (seven to eight hours in bed, achieving about seven hours of sleep), followed by a thirty – to sixty -minute nap in the afternoon.
Biphasic sleep is biological, not cultural. All humans have a genetically hardwired dip in alertness in the mid-afternoon hours.
Our life is shortened when our sleep pattern moves from biphasic sleep to monophasic sleep.

Sleep Cycle

Sleep is divided into two broad phases – NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement).

NREM is also referred to as Deep Sleep.
REM is also referred to as Dreaming Sleep.

We flip-flop between NREM and REM sleep throughout the night every ninety minutes.
The ratio of NREM sleep to REM sleep changes across the night – the initial portion is heavy on NREM, and towards the early hours of the morning, REM prevails.
REM sleep (or dreaming sleep) is also called paradoxical sleep: the brain appears awake to scans, but the body is asleep.

Individual parts of the brain are up to 30 percent more active during REM sleep than when awake!

As you pass into NREM sleep, some of the muscle tension disappears.
During REM sleep, your body is paralyzed, triggered by a powerful disabling signal from your brain stem through the full length of your spinal cord. The brain paralyzes the body to prevent us from acting out the dream – so the mind can dream safely.

Brain’s Information Processing Functions

Wake state can be considered principally as reception

It experiences and continuously learns the world around you.

NREM sleep can be considered as a reflection

It stores and strengthens new facts and skills from your conscious experiences.
NREM sleep helps transfer and safely store newly learned information into long-term storage sites of the brain.

REM sleep can be considered as integration

It interconnects new facts and skills with each other and with all past experiences.
It takes these freshly minted memories and begins colliding them with the entire back catalog of your life’s autobiography.
Mnemonic collisions during REM sleep spark new creative insights as novel links are forged between unrelated pieces of information.
Sleep cycle by sleep cycle, REM sleep helps construct vast associative networks of information within the brain.

Our autobiographical sculpture of stored experience is never complete. Hence the brain requires a new bout of sleep and its stages each night to auto-update our memory based on the events of the previous day.

Animal Kindom and Sleep

An increasingly complex nervous system demands more sleep.

Elephants need just four hours of sleep each day.
Tigers and lions need fifteen hours of daily sleep.
Humans need eight hours of sleep daily.
Other primates sleep ten to fifteen hours daily.
Not all species experience all stages of sleep.
NREM sleep was first to appear in evolution.
Every species experiences NREM sleep.
Only birds and mammals, which appeared later in the evolutionary timeline of the animal kingdom, have full-blown REM sleep.
Humans have 20 and 25 percent of sleep time dedicated to REM sleep, compared to around 9 percent in other primates.

Sleep in Different Stages of our Life

Before Birth

A human infant spends most of its time in a sleep-like state that resembles the REM sleep.
The ‘kicks’ that mothers feel from her baby are likely to be due to random bursts of brain activity from REM sleep. In the safety of the womb, the unborn babies don’t have their body paralyzed during REM sleep.
Typical split of sleep – six hours NREM, six hours REM, and remaining twelve hours in an intermediate sleep state.
Detailed creation of the brain and its components occurs during the second and third trimesters of human development – precisely the time window when REM-sleep increases.
In the last two weeks of pregnancy, the fetus consumes almost nine hours of REM sleep a day.
In the last week before birth, the REM-sleep amount hits a lifetime high of twelve hours a day.

During Childhood

Newborns will typically transition straight into REM sleep after a feeding.
Blocking or reducing REM sleep in newborns prevents and distorts brain development, leading to a socially abnormal adult.
Infants and young kids display polyphasic sleep: many short bouts of sleep through the day and night, punctuated by numerous awakenings.
Only by three or four months of age will a newborn show signs of being governed by a daily rhythm.
By the one-year milestone, the suprachiasmatic nucleus clock of an infant has taken charge of the circadian rhythm.
By four years of age, the circadian rhythm is in dominant command of a child’s sleep behavior, which is usually biphasic.
Late childhood brings about the monophasic pattern of sleep.
The proportion of REM sleep decreases in early childhood, while the portion of NREM sleep increases, even though total sleep time decreases. This proportion stabilizes to 80/20 NREM/REM sleep split by the late teen years.

During Adolescence

The initial brain wiring during childhood is purposefully generous.

During late childhood and adolescence, the second round of remodeling takes place to scale back for efficiency and effectiveness. This remodeling takes the form of pruning of brain connections. The brain uses NREM sleep to help with the job of refinement and downscaling of connectivity.

Why do most 16-year-olds drive like they’re missing part of their brain?
Because they are.

Adolescents have a less rational version of an adult brain, prone to more risk-taking and poor decision-making skills. As deep NREM sleep performs its final overhaul and refinement of the brain during adolescence, cognitive skills, reasoning, and critical thinking start to improve.

The circadian rhythm of a young child runs on an earlier schedule.

Children become sleepy earlier and wake up earlier than their adult parents.
During adolescence, the suprachiasmatic nucleus clock shifts forward so far ahead that it passes even the timing of their adult parents.
Asking your teenage son or daughter to go to bed and fall asleep at ten p.m. is the circadian equivalent of asking you, their parent, to go to sleep at seven or eight p.m. (I have stopped asking my teenaged son to go to bed early!)
Societal and parental attitudes don’t accept that teenagers need more sleep than adults and that they are biologically wired to obtain their sleep at a different time from their parents.
As they age into young adults, their circadian schedule will slide back in time.

During Mid-life and Old Age

During the fourth decade of life, there is a reduction in the electrical quantity and quality of deep NREM sleep.

Age will strip you of 60 to 70 percent of the deep sleep you were enjoying as a young teenager due to the deterioration of deep-sleep-generating regions – the middle-frontal regions seated above the bridge of the nose.
The older we get, the more frequently we wake up in the night. Due to sleep fragmentation, older individuals will experience reduced sleep efficiency.
Older adults appear to need just as much sleep as they do in mid-life, but are simply less able to generate that sleep.
Seniors commonly experience a regression in sleep timing, leading to earlier and earlier bedtimes and also wake up early in the morning.
Dozing off in the evening, which most older adults do not consider as napping, can be the source of sleep difficulty. But this is not insomnia.
The strengths of the circadian rhythm and amount of nighttime melatonin released reduce as we age.

Jet Lag and Sleep

Jet travel causes a biological time lag.

You feel tired and sleepy during the day in the new time zone because your body clock and associated biology still ‘think’ it is nighttime.

At night, you are frequently unable to sleep because your biological rhythm still believes it to be daytime.

For every day you are in a different time zone, your suprachiasmatic nucleus can only re-adjust by about one hour.

It feels harder to acclimate to a new time zone when traveling eastward than when flying westward.

Eastward travel requires you to fall asleep earlier than you would normally, which is a tall ask biologically.
Westward travel requires you to stay up till later, which is a much easier prospect.

Caffeine and Sleep

You can artificially mute the sleep signal of adenosine by using a chemical that makes you feel more alert and awake: caffeine.

Caffeine is the most widely used (and abused) psychoactive stimulant; it represents one of the longest and largest unsupervised drug studies ever conducted on the human race.

Caffeine works by latching on to adenosine welcome sites – or receptors – in the brain.

Caffeine tricks you into feeling alert and awake, despite the high levels of adenosine that would otherwise seduce you into sleep.

Caffeine peaks in our body thirty minutes after oral administration.
It has an average half-life (time to remove half of the caffeine in the body) of five to seven hours.
Sleep will not come quickly or be smooth throughout the night as your brain continues its battle against the opposing force of caffeine.

For the entire time that caffeine is in your system, the sleepiness chemical it blocks (adenosine) nevertheless continues to build up. Once your liver dismantles that barricade of caffeine, you are hit with the sleepiness you had experienced two or three hours ago before you drank that cup coffee. This is called a caffeine crash.

Remember – ‘No child needs caffeine.’

Alcohol and Sleep

Many people believe alcohol helps them to fall asleep more quickly, or even offers sounder sleep.

Alcohol is in a class of drugs called sedatives. It binds to receptors within the brain that prevent neurons from firing their electrical impulses.

Your increased sociability is caused by sedation of one part of your brain, the prefrontal cortex (seat of rational, logical thinking), early in the timeline of alcohol’s creeping effects.

Alcohol sedates you out of wakefulness, but it does not induce natural sleep.

Alcohol-induced sleep is more like a light form of anesthesia.
Alcohol fragments sleep, littering the night with brief awakenings.
Alcohol is one of the most powerful suppressors of REM sleep that we know of. When the body metabolizes alcohol, it produces by-product chemicals called aldehydes and ketones. The aldehydes, in particular, will block the brain’s ability to generate REM sleep. The pent-up REM-sleep pressure, built up due to alcohol, can force itself into waking consciousness, causing hallucinations, delusions, and gross disorientation.
Alcohol consumption by an expecting mother significantly reduced the amount of time unborn babies spent in REM sleep, relative to the non-alcohol condition.
Sleep deprivation, with only four hours of sleep, plus the effect of alcohol, caused a group of people in a research study to drive off the road thirty times more than the well-rested, sober group.
People in a study had their sleep laced with alcohol on the first night after learning. They suffered partial amnesia seven days later, forgetting more than 50 percent of all that original knowledge.
People with two full nights of natural sleep after initial learning had their sleep doused with alcohol on the third night. This resulted in almost the same degree of amnesia – 40 percent of the knowledge established on day one was forgotten.
Memories remain perilously vulnerable to any disruption of sleep (including that from alcohol) even up to three nights after learning, despite two full nights of natural sleep prior.
Nightly alcohol will disrupt your sleep. Abstinence is the best advice if you love your sleep.

(Politically incorrect advice: If you need to drink, go to the pub for a drink in the morning. That way, the alcohol will be out of your system before sleep.)

Naps

Napping before a bout of sleep deprivation could add a temporary and partial buffer that can protect the brain from suffering catastrophic lapses in concentration.

Power naps (term arises from the airline industry; read the book for details) may momentarily increase basic concentration under conditions of sleep deprivation, as can caffeine up to a specific dose.
Neither naps nor caffeine can salvage more complex functions of the brain, including learning, memory, emotional stability, complex reasoning, or decision-making.
There is but a fraction of 1 percent of the population who are genuinely resilient to the effects of chronic sleep restriction at all levels of brain function. It is far more likely for lightning to strike you than for you to be part of this fraction of 1 percent.

Food and Sleep

When food becomes scarce, sleep becomes scarce, as animals try to stay awake longer to forage.

Part of the reason that these hunter-gatherer tribes are not obese is that they are continually searching for food. Place an organism under conditions of severe famine, and foraging for food will supersede sleep.

Individuals who are deliberately fasting will sleep less as the brain is tricked into thinking that food has suddenly become scarce.

For healthy sleep, the scientific evidence suggests that you should

avoid going to bed too full or too hungry, and
shy away from diets that are excessively biased toward carbohydrates (greater than 70 percent of all energy intake), especially sugar.

Alarm Clocks and Sleep

Participants in study artificially wrenched from sleep by an alarm going off will suffer a spike in blood pressure and a shock acceleration in heart rate.

If you use an alarm clock, avoid using the snooze function. Get in the habit of waking up only once to spare your heart the repeated shock.

Sleeping Pills

No drug has the proven ability to replace those benefits that a full night of sleep infuses into the brain and body.

Sleeping pills do not provide natural sleep, can damage health, and increase the risk of life-threatening diseases.

Sleeping pills effectively knock out the higher regions of your brain’s cortex.
The electrical type of sleep these drugs produce lacks in the largest, deepest brainwaves.
The majority of prescription sleeping pills are in a class of physically addictive drugs.
There was no difference in how soundly the individuals slept. A study found that both the placebo and the sleeping pills reduced the time it took people to fall asleep (between ten and thirty minutes), but the change was not statistically different between the two.
Sleeping-pill laced sleep is a memory eraser, rather than engraver. Users of sleeping pills may fall asleep nominally faster at night; they should expect to wake up with fewer memories of yesterday.
Individuals using prescription sleep medications are significantly more likely to die and to develop cancer than those who do not.
Individuals classified as heavy users (defined as taking more than 132 pills per year) were 5.3 times more likely to die over the study period.
Even very occasional users (defined as taking just eighteen pills per year) were still 3.6 times more likely to die at some point.

No study to date has shown that sleeping pills save lives.

Exercise and Sleep

Sleep and physical exertion have a bidirectional relationship. Sleep may have more of an influence on exercise than exercise has on sleep.

In younger, healthy adults, exercise frequently increases total sleep time, especially deep NREM sleep.

Unexpected, however, was the lack of a tight relationship between exercise and subsequent sleep from one day to the next. When sleep was poor the night prior, exercise intensity and duration were far worse the following day.

Try not to exercise right before bed.
Body temperature can remain high for an hour or two after physical exertion.
Should this occur too close to bedtime, it can be difficult to drop your core temperature sufficiently to initiate sleep.

Sleep and Work

The loud-and-proud corporate mentality of sleeplessness as the model for success is evidentially wrong at every level.

Studies have shown that:

Sleepy employees are unproductive employees.
Sleep-deprived individuals generate fewer and less accurate solutions to work-relevant problems.
Individuals who obtained less sleep in the preceding days are the same people who consistently select less challenging problems. They opt for the easy way out, generating fewer creative solutions in the process.
Even the simplest daily routines that require slight effort, such as time spent dressing neatly or fashionably for the workplace, have been found to decrease following a night of sleep loss.
When you are not getting enough sleep, you work less productively and thus need to work longer to accomplish a goal.
In the days after a supervisor had slept poorly, the employees themselves, even if well-rested, became less engaged in their jobs.
Under-slept managers and CEOs are less charismatic.

Am I Getting Enough Sleep?

The shorter your sleep, the shorter your life.

First, after waking up in the morning, could you fall back asleep at ten or eleven a.m.? If the answer is ‘yes,’ you are likely not getting sufficient sleep quantity and/or quality.

Second, can you function optimally without caffeine before noon? If the answer is ‘no,’ then you are most likely self-medicating your state of chronic sleep deprivation.

If you didn’t set an alarm clock, would you sleep past that time? If so, you need more sleep than you are giving yourself.

Do you find yourself at your computer screen reading and then rereading (and perhaps rereading) the same sentence? This is often a sign of a fatigued, under-slept brain.

Do you sometimes forget what color the last few traffic lights were while driving? Simple distraction is often the cause, but a lack of sleep is very much another culprit.

Below is SATED, a simple questionnaire developed by sleep researchers to determine your degree of sleep fulfillment.

Twelve Tips for Healthy Sleep

Stick to a sleep schedule. Go to bed at the same time every night and wake up at the same time.
Exercise is great, but not too late in the day. You should not exercise within 2-3 hours before sleep to ensure your core body temperature drops to initiate sleep.
Avoid caffeine and nicotine. Coffee, colas, certain teas, and chocolate contain the stimulant caffeine, and its effects can take as long as eight hours.
Avoid alcoholic drinks before bed.
Avoid large meals and beverages late at night.
If possible, avoid medicines that delay or disrupt your sleep.
Don’t take naps after 3 p.m.
Relax before bed. Don’t over-schedule your day so that no time is left for unwinding. A relaxing activity, such as reading or listening to music, should be part of your bedtime ritual.
Take a hot bath before bed.
Dark bedroom, cool bedroom, gadget-free bedroom.
Have the right sunlight exposure. Try to get outside in natural sunlight for at least thirty minutes each day. Even sunlight coming through thick clouds on a rainy day is powerful enough to help reset our biological clocks.
Don’t lie in bed, awake. If you find yourself still awake after staying in bed for more than twenty minutes or if you are starting to feel anxious or worried, get up and do some relaxing activity until you feel sleepy.

If there is only one tip you can follow, then follow the first one.

Sleeping Tips for the Elderly

Two tips for seniors to adjust their body clock to later time (to avoid sleeping too early and waking up too early)

First, wear sunglasses during morning exercise outdoors.
Second, go back outside in the late afternoon for sunlight exposure, but this time do not wear sunglasses.

Safety tips for the elderly

Have a side lamp within reach that you can switch on easily,
Use dim or motion-activated night-lights in the bathrooms and hallways to illuminate your path,
Remove obstacles or rugs en route to the bathroom to prevent stumbles or trips, and
Keep a telephone by your bed with emergency phone numbers programmed on speed dial.

Common Myths to Overcome Drowsiness while Driving

Turning up the radio
Winding down the car window
Blowing cold air on your face
Splashing cold water on your face
Talking on the phone
Chewing gum
Slapping yourself, pinching yourself, punching yourself, and promising yourself a reward for staying awake.

None of these are useful in overcoming drowsiness while driving. If you feel sleepy, pull over to a rest area and take a nap.

Constant Electric Light and Sleep

By delaying the release of melatonin, artificial evening light makes it considerably less likely that you’ll be able to fall asleep at a reasonable time.

Even a hint of dim light – 8 to 10 lux – has been shown to delay the release of nighttime melatonin in humans. The feeblest of bedside lamps pumps out twice as much: anywhere from 20 to 80 lux.
The light receptors in the eye that communicate ‘daytime’ to the suprachiasmatic nucleus are most sensitive to short-wavelength light within the blue spectrum- the exact spot where blue LEDs are most powerful. Hence, evening blue LED light has twice the harmful impact on nighttime melatonin suppression.
Using an iPad for two hours before bed blocked the otherwise rising levels of melatonin by a significant 23 percent.
Compared to reading a printed book, reading on an iPad suppressed melatonin release by over 50 percent at night.
A good start is to create lowered, dim light in the rooms where you spend your evening hours.
You can install software on your computers, phones, and tablet devices that gradually de-saturate the harmful blue LED light as the evening progresses.
Use blackout curtains.

Regularized Temperature and Sleep

Core temperature needs to decrease by 2 to 3 degrees Fahrenheit, or about 1 degree Celsius, to initiate sleep successfully.

You will always find it easier to fall asleep in a room that is too cold than too hot.
Your nocturnal melatonin levels are therefore controlled not only by the loss of daylight at dusk but also the drop in temperature that coincides with the setting sun.
The hands, feet, and head are therefore remarkably efficient radiating devices that, just before sleep onset, jettison body heat in a massive thermal venting session to drop your core body temperature.
Warm hands and feet help your body’s core cool. Selectively warming the feet and hands by just a small amount (1°F, or about 0.5°C) caused a local swell of blood to these regions, thereby charming heat out of the body’s core.
A bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people, assuming standard bedding and clothing.
Bereft of the natural drop in evening temperature, our brains do not receive the cooling instruction within the hypothalamus that facilitates a naturally timed release of melatonin.
Hot baths before bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults.

Sleep is the most powerful elixir of wellness and vitality, dispensed through every conceivable biological pathway.