The Science of Sleep: A Brief Guide on How to Sleep Better Every Night

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https://jamesclear.com/sleep

 

The Science of Sleep: A Brief Guide on How to Sleep Better Every Night

If you want to learn how to sleep better, then you’re in the right place. This guide will walk you through everything you need to know if you want to get better sleep. I’ll explain the science of sleep and how it works, discuss why many people suffer from sleep deprivation without knowing it, and offer practical tips for getting better sleep and having more energy.

Plain and simple, the purpose of this guide is to explain the science of how to sleep better. You can click the links below to jump to a particular section or simply scroll down to read everything. At the end of this page, you’ll find a complete list of all the articles I have written on sleep.

I. The Science of Sleep

II. How Sleep Works

III. How to Sleep Better

 

I. The Science of Sleep

Sleep is one of the strangest things we do each day. The average adult will spend 36 percent of his or her life asleep. For one-third of our time on earth, we transition from the vibrant, thoughtful, active organisms we are during the day and power down into a quiet state of hibernation.

But what is sleep, exactly? Why is it so important and so restorative for our bodies and minds? How does it impact our lives when we are awake?

The Purpose of Sleep

Sleep serves multiple purposes that are essential to your brain and body. Let’s break down some of the most important ones.

The first purpose of sleep is restoration. Every day, your brain accumulates metabolic waste as it goes about its normal neural activities. While this is completely normal, too much accumulation of these waste products has been linked to neurological disorders such as Alzheimer’s disease.

Alright, so how do we get rid of metabolic waste? Recent research has suggested that sleep plays a crucial role in cleaning out the brain each night. While these toxins can be flushed out during waking hours, researchers have found that clearance during sleep is as much as two-fold faster than during waking hours.

The way this process occurs is fairly remarkable:

During sleep, brain cells actually shrink by 60 percent, allowing the brain’s waste-removal system—called the glymphatic system—to essentially “take out the trash” more easily. The result? Your brain is restored during sleep, and you wake up refreshed and with a clear mind.

The second purpose of sleep is memory consolidation. Sleep is crucial for memory consolidation, which is the process that maintains and strengthens your long-term memories. Insufficient or fragmented sleep can hamper your ability to form both concrete memories (facts and figures) and emotional memories.

Finally, sleep is paramount for metabolic health. Studies have shown that when you sleep 5.5 hours per night instead of 8.5 hours per night, a lower proportion of the energy you burn comes from fat, while more comes from carbohydrate and protein. This can predispose you to fat gain and muscle loss. Additionally, insufficient sleep or abnormal sleep cycles can lead to insulin insensitivity and metabolic syndrome, increasing your risk of diabetes and heart disease.

All of this to say, that better sleep is critical for your mental and physical health. Before we get too deep into this sleep guide though, let’s pause for just a second. If you’re enjoying this article on sleep, then you’ll probably find my other writing on performance and human behavior useful. Each week, I share self-improvement tips based on proven scientific research through my free email newsletter.

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How Much Sleep Do You Need?

Alright, so sleep is important, but how much sleep do you really need? To answer that question, let’s consider an experiment conducted by researchers at the University of Pennsylvania and Washington State University.

The researchers began the experiment by gathering 48 healthy men and women who had been averaging seven to eight hours of sleep per night. Then, they split these subjects into four groups. The first group had to stay up for 3 days straight without sleeping. The second group slept for 4 hours per night. The third group slept for 6 hours per night. And the fourth group slept for 8 hours per night. In these final three groups—4, 6, and 8 hours of sleep—the subjects were held to these sleep patterns for two weeks straight. Throughout the experiment the subjects were tested on their physical and mental performance. 

The Cost of Sleep Deprivation

The irony of it all is that many of us are suffering from sleep deprivation so that we can work more, but the drop in performance ruins any potential benefits of working additional hours.

In the United States alone, studies have estimated that sleep deprivation is costing businesses over $100 billion each year in lost efficiency and performance. 

Here’s a useful analogy for why sleep is so important.

The Theory of Cumulative Stress

Imagine that your health and energy are a bucket of water. In your day-to-day life, there are things that fill your bucket up. Sleep is one of the main inputs. These are also things like nutrition, meditation, stretching, laughter, and other forms of recovery.

There are also forces that drain the water from your bucket. These are outputs like lifting weights or running, stress from work or school, relationship problems, or other forms of stress and anxiety. 

The forces that drain your bucket aren’t all negative, of course. To live a productive life, it can be important to have some of those things flowing out of your bucket. Working hard in the gym, at school, or at the office allows you to produce something of value. But even positive outputs are still outputs and they drain your energy accordingly.

These outputs are cumulative. Even a little leak can result in significant water loss over time.

Keeping Your Bucket Full

If you want to keep your bucket full, you have two options.

  1. Refill your bucket on a regular basis. That means making time for sleep and recovery.
  2. Let the stressors in your life accumulate and drain your bucket. Once you hit empty, your body will force you to rest through injury and illness.

Recovery is not negotiable. You can either make time to rest and rejuvenate now or make time to be sick and injured later. Keep your bucket full.

Ok, But Can You Catch Up on Sleep?

Extra sleep can remedy some of the negative effects of several bad nights of sleep. New research found that catching up on sleep on the weekends brought daytime sleepiness and inflammation levels back to baseline; however, cognitive performance did NOT rebound.

What exactly does that mean? If you’re not getting enough sleep during the week, you cannot depend on catch-up sleep on the weekends to restore your focus and attention. The only way to keep levels of those performance measures high is to make sure you’re getting adequate sleep every night.

Now does this mean you shouldn’t even try to catch up on sleep? No. If you’re already sleep deprived, you should definitely try to get some extra sleep. But the best thing to do, both for immediate performance and for the long-term, is to prioritize sleep every night—not just on the weekends. 

II. How Sleep Works

The Sleep-Wake Cycle

The quality of your sleep is determined by a process called the sleep-wake cycle.

There are two important parts of the sleep-wake cycle:

  1. Slow wave sleep (also known as deep sleep)
  2. REM sleep (REM stands for Rapid Eye Movement)

During slow wave sleep the body relaxes, breathing becomes more regular, blood pressure falls, and the brain becomes less responsive to external stimuli, which makes it more difficult to wake up. This phase is critical for renewal and repair of the body. During slow wave sleep, the pituitary gland releases growth hormone, which stimulates tissue growth and muscle repair. Researchers also believe that the body’s immune system is repaired during this stage. Slow wave sleep is particularly critical if you’re an athlete. You’ll often hear about professional athletes like Roger Federer or LeBron James sleeping 11 or 12 hours per night. 

Age-Related Sleep Changes

According to Harvard Medical School researchers, “As people age, it takes longer to fall asleep, a phenomenon called increased sleep latency. And sleep efficiency – the percentage of time spent asleep while in bed – decreases as well.”

Learn how to sleep better by understanding sleep cycle changes and age

Based on my calculations of the above data, the average 80-year-old gets a whopping 62 percent less slow wave sleep than the average 20-year-old (20 percent of the average sleep cycle versus 7.5 percent). There are many factors that impact the aging of body tissues and cells, but it stands to reason that if your body gets less slow wave sleep to restore itself each night, then the aging process will accelerate as a result.

In other words, it seems reasonable to say that getting good sleep is one of your best defenses against aging quickly.

The Circadian Rhythm

What is your sleep-wake cycle dictated by?

Answer: the circadian rhythm. The circadian rhythm is a biological cycle of different processes that happen over a time span of about 24 hours.

Learn how to sleep better by understanding the circadian rhythm

Here are some key points in the typical 24-hour cycle:

  • 6 A.M. Cortisol levels increase to wake your brain and body
  • 7 A.M. Melatonin production stops
  • 9 A.M. Sex hormone production peaks
  • 10 A.M. Mental alertness levels peak
  • 2:30 P.M. Best motor coordination
  • 3:30 P.M. Fastest reaction time
  • 5 P.M. Greatest cardiovascular efficiency and muscle strength
  • 7 P.M. Highest blood pressure and body temperature
  • 9 P.M. Melatonin production begins to prepare the body for sleep
  • 10 P.M. Bowel movements suppressed as the body quiets down
  • 2 A.M. Deepest sleep
  • 4 A.M. Lowest body temperature

Obviously, these times are not exact and merely display the general pattern of the circadian rhythm. The exact times of your circadian rhythm will vary based on daylight, your habits, and other factors we will discuss later in this guide.

The circadian rhythm is impacted by three main factors: light, time, and melatonin.

Light. Light is probably the most significant pace setter of the circadian rhythm. Staring into a bright light for 30 minutes or so can often reset your circadian rhythm regardless of what time of day it is. More commonly, the rising of the sun and light striking your eyes triggers the transition to a new cycle.

Time. The time of day, your daily schedule, and the order in which you perform tasks can all impact your sleep-wake cycle.

Melatonin. This is the hormone that causes drowsiness and controls body temperature. Melatonin is produced in a predictable daily rhythm, increasing after dark and decreasing before dawn. Researchers believe that the melatonin production cycle helps keep the sleep-wake cycle on track.

The 2-Process Model of Sleep Regulation

In 1982, Dr. Alexander Borbely published an article in the journal Human Neurobiology describing something he called the 2-process model of sleep regulation. This conceptual framework for sleep describes two processes that occur simultaneously to regulate sleep and wake states.

Process 1 is sleep pressure. Basically, sleep pressure mounts from the moment you wake up, to the time when you go to sleep. While you’re sleeping, pressure decreases. If you get a full night of sleep, you start the next day with low sleep pressure.

Process 2 is wake drive, which counteracts sleep pressure and is controlled by a 24-hour rhythm that repeats in a wave-pattern.

It’s important to understand this process because it helps reveal an important point about sleep in our modern world that I learned from sleep scientist Dan Pardi:

For millions of years, humans and our ancestors have evolved to sleep at night (when it is dark) and wake during the day (when it is light). However, in the modern world, we work inside all day, often in areas that are darker than the outside world. And then, at night, we look at bright screens and televisions. Low light during the day, more light at night: It’s the opposite of naturally occurring cycles and it seems quite likely that it could mess up your wake rhythm and circadian rhythm.

III. How to Sleep Better

How to Fall Asleep Fast

Develop a “power down” ritual before bed. The light from computer screens, televisions, and phones can hinder the production of melatonin, which means your body isn’t preparing the hormones it needs to enter the sleep phase. Specifically, it is the blue wavelength of light that seems to decrease melatonin production. Developing a “power down” routine where you shut off all electronics an hour or two before sleep can be a big help. Additionally, working late at night can keep your mind racing and your stress levels high, which also prevents the body from calming down for sleep. Turn off the screens and read a book instead. It’s the perfect way to learn something useful and power down before bed. (Another option is to download an app called f.lux, which reduces the brightness of your screen closer to bedtime.)

Use relaxation techniques. Researchers believe that at least 50 percent of insomnia cases are emotion or stress related. Find outlets to reduce your stress and you’ll often find that better sleep comes as a result. Proven methods include daily journaling, deep breathing exercises, meditation, exercise, and keeping a gratitude journal (write down something you are thankful for each day).

How to Improve Sleep Quality and Duration

If you want to know how to sleep better and boost your performance there are 3 levers you can “pull” to give yourself a boost.

  1. Intensity
  2. Timing
  3. Duration

Intensity refers to how well you sleep. The percentage of sleeping time you spend in slow wave sleep and REM sleep largely determine the quality of your sleep each night. 

Daily Habits for Better Sleep

Next, let’s talk about how to sleep better by harnessing the power of a few simple, daily habits.

Get outside. Aim for at least 30 minutes of sun exposure each day.

Turn out the lights. When it gets dark outside, dim the lights in your house and reduce blue or full-spectrum light in your environment. F.lux, a free software app for your computer, makes the color of your computer’s display adapt to the time of day, warm at night and like sunlight during the day.

Avoid caffeine. If you’re having trouble falling asleep, eliminating caffeine from your diet is a quick win. If you can’t go without your morning cup of coffee, then a good rule of thumb to keep in mind is “No coffee after noon.” This gives caffeine enough time to wear off before bed time.

Stop smoking or chewing tobacco. Tobacco use has been linked to a long line of health issues, and poor sleep is another one on the list. I don’t have any personal experience with tobacco use, but I have heard from friends who have quit successfully that Allen Carr’s Easy Way to Stop Smoking book is the best resource on the topic.

Use the bedroom for sleep and sex only. Is your bedroom designed to promote good sleep? The ideal sleeping environment is dark, cool, and quiet. Don’t make your bedroom a multi-purpose room. Eliminate TVs, laptops, electronics, and clutter. These are simple ways to improve the choice architecture of your bedroom, so that sleep is easier and distraction is harder. When you go to the bedroom, go there to sleep.

Natural Sleep Aids

Exercise. There are too many benefits to exercise to list them all here. When it comes to sleep, exercise will make it easier for your brain and body to power down at night. Furthermore, obesity can wreak havoc on your sleep patterns. The role of exercise only becomes more important with age. Fit middle-aged adults sleep significantly better than their overweight peers. One caveat: avoid exercising two to three hours before bedtime as the mental and physical stimulation can leave your nervous system feeling wired and make it difficult to calm down at night.

Temperature. Most people sleep best in a cool room. The ideal range is usually between 65 to 70 degrees Fahrenheit (18 to 21 degrees Celsius).

Sound. A quiet space is key for good sleep. If peace and quiet is hard to come by, try controlling the bedroom noise by creating “white noise” with a fan. Or, use ear plugs (here’s a good pair).

Alcohol. This one is a slippery slope. It is true that having a drink before bed — a “night cap” — often does help people fall asleep. However, while it makes it easier to fall asleep, it actually reduces the quality of your sleep and delays the REM cycle. So you fall asleep faster, but it’s possible that you’ll wake up without feeling rested. It’s probably best to improve your sleep through other methods before resorting to alcohol to do the job.

Final Thoughts on How to Sleep Better

Cumulative sleep debt is a barrier between you and optimal performance. If you want to know how to sleep better, the answer is simple but remarkably underrated in our productivity-obsessed culture: get more sleep.

All Sleep Articles

This is a complete list of articles I’ve written on sleep. Enjoy!

FOOTNOTES
  1. The cumulative cost of additional wakefulness
  2. How Little Sleep Can You Get Away With?
  3. Functional and Economic Impact of Sleep Loss and Sleep-Related Disorders
  4. The remaining 5 percent are due to genetic variations that allow them to perform optimally on less sleep. Obviously, it is unlikely that you or I have been dealt such a favorable genetic hand.
  5. My image of the bucket was inspired by the original idea of the stress and recovery bucket mentioned in Paul Chek’s book, How to Eat, Move and Be Healthy!
  6. Thanks to Mark Watts for originally sharing with me the idea that stress is cumulative.
  7. More on that study in this article: Can You Ever REALLY Catch Up on Sleep?
  8. Don’t you find it interesting that many of the best athletes in the world sleep at least 10 hours per night? Wouldn’t you assume that if anyone had access to the latest biohacking technology and advanced sleeping tactics, it would be the world’s greatest athletes? If there was any group of people who could afford the research and money to purchase the best ways to hack their sleep and get more done in less time, it would be this group. They could use this time for increased training, additional practice, and so on. And yet, sleeping more is what provides them greater value. I mention this because it can be easy for us to look for a quick fix, a “biohack” that allows us to somehow master the puzzle of sleep and get more done. But when you look at the world’s greatest performers you see that the answer is very simple: sleep more
  9. The Effects of Sleep Extension on the Athletic Performance of Collegiate Basketball Players
  10. More in the first half of this article by Dan Pardi
  11. Improving Sleep: A guide to a good night’s rest, a Harvard Medical School publication
  12. The Effects of Sleep Extension on the Athletic Performance of Collegiate Basketball Players
  13. Improving Sleep: A guide to a good night’s rest, a Harvard Medical School publication
  14. Thanks to Dan Pardi for telling me about the 3 levers of sleep.
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