The Ultimate Guide to Sleep - What Science Says About Sleep Deprivation and What You Can Do About It

Lack of sleep and chronic sleep deprivation have disastrous effects on our health. Yet in a go-go-go society, sleep is one of the easiest things to give up. The goal of this article is to educate you about sleep. It will cover the epidemiology of sleep deprivation. It will explain what happens to our bodies when we are sleep deprived. It will explore how sleep deprivation affects our health. Finally, it will provide information on how to fall asleep easier.


Topics covered

Circadian rhythm and chronotypes

Teenagers and sleep

Adenosine and caffeine

Sleep deprivation symptoms

Sleep stages and alcohol

Sleep aids and medications

Cognitive behavior therapy for insomnia, sleep hygiene, and tips to fall asleep faster


The benefits of sleep is not a secret


Sleep is not a secret to athletes performing on the world’s biggest stages. All time great athletes have touted the benefits of sleep. These include athletes such as Tom Brady, Lebron James, Roger Federer, and Michael Phelps. Usain Bolt, an 8 time olympic gold medalist said, "sleep is extremely important to me. I need to rest and recover in order for the training I do to be absorbed by my body."


So where is the disconnect between what athletes know to be true and what we do in our daily lives?


How much sleep do we need


The National Sleep Foundation recommends adults get 7-9 hours of sleep per night. But in 2014, the CDC reported 35.2% of US adults slept less than 7 hours per night. This is an alarming public health crisis. Sleep deprivation has major consequences on health and health outcomes. This includes cardiovascular disease, diabetes, and metabolic syndrome. It affects dementia and psychiatric conditions. Chronic sleep deprivation even increases all-cause mortality.


Circadian rhythm definition and sleep cycle


We need to first understand what sleep actually is. Let’s start with our circadian rhythm. You can think of the circadian rhythm as our internal clock that regulates how alert we are. It rises in the morning after we wake up. It then dips in the early afternoon and rises again towards evening. Then it drops at night.


Our circadian rhythms will go through this cycle regardless how much sleep we get. The average duration of an adult’s circadian rhythm is around 24 hours. This aligns well with the length of a day.


What is a chronotype?


It’s important to point out that everyone’s circadian rhythm is different. We call these differences chronotypes. Some people are early risers and some are night owls. Your genetics play a role in determining what type you are. About 40% of the population are morning types. 30% of the population are evening types The last 30% are somewhere between with a lean towards the evening. That’s about 60% of the population that skew towards an evening chronotype.


Chronotype and health


Even something as simple as your chronotype can play a major role for your health. Population studies have shown that people with evening types have higher health risks. Here is a sample of the growing amount of scientific literature on chronotypes.


  • These researchers reported that “evening chronotype was independently associated with diabetes, metabolic syndrome, and sarcopenia.”

  • This group found that “greater eveningness was associated with a small increased risk of all-cause mortality and cardiovascular disease mortality.”

  • This article writes “while evening chronotype is most consistently associated with severity of mood disorder symptoms, emerging evidence implicates evening chronotype as a transdiagnostic correlate of substance use severity, anxiety symptoms, attentional difficulties, and maladaptive behaviors such as aggression.”

  • These researchers found that “evening chronotype may be an independent risk factor for breast cancer.”


To summarize, having an evening chronotype will affect your risk factor for diseases. This includes cardiovascular disease, diabetes, cancer, and mental health disorders. It may even increase your all cause mortality.


Circadian rhythm changes with age


This article describes how our circadian rhythm changes as we grow. Infants need a lot of sleep - anywhere between 12-15 hours per day. Preschoolers need 10-13 hours per day. Adolescents need 8-10 hours per day. Adults need 7-9 hours per day.


Infants, toddlers, and preschoolers go to bed early compared to adults. This is because they have an early chronotype. As infants age, their chronotype shifts so that their bedtime is later in the evening. This continues to the teenage years. In fact, teenagers tend to go to bed later than most adults. As they become young adults, they end up at their genetic predetermined chronotype.


How much sleep do teenagers need?


Let’s take a detour to examine how adolescent chronotypes affect teenagers’ health. Teenagers tend to go to bed past midnight and wake up late in the morning. If left to sleep and wake up on their own, they will feel tired around 11pm and wake up after 8am. This is due to their circadian rhythm and their adolescent chronotype.


But this is actually a major problem in today’s society. Teenagers often need to get to school by 8am. This means waking up by 7am or even earlier. To wake up by 7am and get the recommended 8-10 hours per night, teenagers need to be in bed around 9-10pm. This is a big problem if most teenagers are going to bed after midnight.


Consensus statements on how much sleep teenagers need


In 2016, the American Academy of Sleep Medicine released a consensus statement about teenager sleep. They state “Sleeping the number of recommended hours on a regular basis is associated with better health outcomes including: improved attention, behavior, learning, memory, emotional regulation, quality of life, and mental and physical health. Regularly sleeping fewer than the number of recommended hours is associated with attention, behavior, and learning problems. Insufficient sleep also increases the risk of accidents, injuries, hypertension, obesity, diabetes, and depression. Insufficient sleep in teenagers is associated with increased risk of self-harm, suicidal thoughts, and suicide attempts.”


The American Academy of Pediatrics also released a consensus statement in 2014. They argue that "middle and high schools should aim for a starting time of no earlier than 830am.” This will help battle adolescent sleep deprivation.


Many school districts have already made changes and their findings are encouraging. These researchers looked at a 45 minute delay in high school start time. They found that “later start times improved tardiness and disciplinary issues.”


This article looked at the effects of a 25 minute delay in school start time. There were “significant improvements in sleep duration, daytime sleepiness, mood, and caffeine use.”


While these studies are encouraging, there is a lot of room for improvement. According to the CDC in 2014, “93% of high schools and 83% of middle schools in the US started before 830am.


Adenosine and sleep pressure


Now we have a basic understanding of circadian rhythms and chronotypes. Let's learn about the other mechanism that determines sleep.


The second factor is called sleep pressure. This is controlled by adenosine. Adenosine is a molecule that accumulates in the brain while we are awake. Peak levels occur around 12-16 hours of being awake. We feel more sleep pressure with higher levels of adenosine. When we sleep, our bodies remove adenosine which causes a drop in sleep pressure. The drop in adenosine coincides with a rise in our circadian rhythm. The two work together to wake us up.


If we get 7-9 hours of continuous sleep, our bodies will have enough time to clear out all the adenosine. But if we sleep only a few hours, adenosine will accumulate. Chronic sleep deprivation leads to persistent elevations in adenosine. This is carried forward as sleep debt.


Caffeine and adenosine


What does caffeine have to do with adenosine? Caffeine is an adenosine receptor antagonist. It binds to the same receptor that adenosine binds to. But it does not activate it.


When adenosine binds to its receptor, it increases sleep pressure. When caffeine binds to the adenosine receptor, nothing happens. Caffeine competes with adenosine. The caffeine from a cup of coffee will stop the effects of adenosine. That's how caffeine energizes you.


But drinking caffeine does nothing to address the accumulating levels of adenosine. Once caffeine wears off, adenosine starts to work again. Adenosine receptors reactivate and you feel the full force of sleep pressure.


Sleep deprivation symptoms and effects on concentration


How does sleep affect our ability to think and concentrate? These researchers first had volunteers establish a cognitive baseline. The subjects took computerized tests measuring reaction speeds, memory, coordination, and perception. The participants were subjected to two conditions: sleep deprivation and alcohol. Their performances were then re-evaluated under each condition.


The authors wrote “as expected, increasing concentrations of alcohol produced significant reductions in performance for most tests and measures.” They also found that sleep deprivation harmed the participants' performances.


Being awake between 17-19 hours gave similar results to a blood alcohol concentration of 0.1%. Recall that in most states, the drunk driving limit is a blood alcohol concentration of 0.08%. So to extrapolate, if you stay awake for 17 hours, your mind is functioning the same as if you were legally drunk.


Many researchers have repeated these experiments. They subject participants to sleep deprivation. They then test their ability to perform on tests. Without fail, the more sleep deprived the participants, the worse they do on tests.


And the effects add up. The more days you are sleep deprived, the worse you perform on tests.


These researchers looked at the effects of chronic sleep restriction on volunteers. They assessed sleep restricted to 4 hours, 6 hours, or 8 hours per night for 14 consecutive days. They even had some volunteers go three straight days without sleeping.


They found that “chronic restriction of sleep periods to 4 hours or 6 hours per night over 14 consecutive days resulted in significant cumulative, dose-dependent deficits in cognitive performance on all tasks.” The volunteers who went sleepless for three days straight had disastrous results. The authors also found that participants who slept 6 hours for 10 nights in a row had the same performance as someone who had not slept in 24 hours.


Let's put everything together now.


We learned that if you don’t sleep for 17 hours, your mind functions as if you were legally drunk. We also learned that if you get 6 hours of sleep for 10 nights in a row, you are performing the same as someone who has not slept in 24 hours. This suggests that if you get 6 hours of sleep for 10 nights in a row, your mind is functioning as if you were legally drunk.


How many people in the United States sleep only 6 hours? In 2014 the CDC reported 35.2% of the US population sleeps less than 7 hours per night. The US had a population of 318.4 million people in 2014. That comes out to 112 million people.


Now I’m not saying every sleep deprived person is legally drunk - it’s not as clear cut as this. Our bodies have an incredible ability to adapt. But you still need to ask yourself. Do you want your body to adapt to this toxic situation?


Sleep deprivation effects on cardiovascular disease


Cardiovascular disease is the number one leading cause of death in the United States. This includes heart attacks and strokes. These researchers looked at 20,000 adults in the Netherlands and followed them for 15 years.


Adults who had short sleep duration had “15% higher risk of total cardiovascular disease and a 23% higher risk of coronary heart disease compared to normal sleepers.” The subjects who felt they did not get good quality sleep had a “63% higher risk for cardiovascular disease and a 79% higher risk for coronary heart disease compared to normal sleepers with good sleep quality.”


What do these numbers mean? Here’s a comparison. We all know smoking is bad for your health. It increases your risk for heart attacks and strokes. Based on recent data, lack of sleep seems to be as bad for your heart as smoking is.


Daylight savings affects sleep


Now the above data is all observational. It’s impossible to perform a randomized controlled trial on sleep over the course of 15 years. Fortunately there is a natural occurring experiment every year in the United States. This experiment links the effects of sleep to cardiovascular disease. What is this experiment?


Daylight savings time.


Every year in the spring, we lose one hour of sleep. And every year in the fall, we gain that hour back. Is there a link between losing one hour of sleep on the rates of heart attacks?


Researchers reviewed hospitalization data the weeks following spring daylight savings time. These researchers performed a meta analysis on seven different studies. They found that “a significantly higher risk of acute myocardial infarction was observed during the two weeks following spring daylight savings transition.”


They concluded losing one hour of sleep increased the risk of a heart attack in the following two weeks. Similar patterns exist for strokes and motor vehicle accidents. In November 2018, a California ballot measure looked to end daylight savings time. It cited significant medical risks associated with time changes. It was not passed. But did voters understand the risks associated with insufficient sleep?


Sleep deprivation effects on cancer


What about cancer? It is the second leading cause of death in the United States. It turns out disordered sleep is not great for that either. The International Agency for Research on Cancer is part of the World Health Organization. They categorized night shift work as a Group 2A carcinogen. This means night shift work is probably carcinogenic to humans. (You will be surprised by what else is on their list.)


The majority of data that supports this comes from two very large population data. These are the Nurses’ Health Study (78,000 nurses) and the Nurses’ Health Study II (114,000 nurses). Nurses work shifts in the hospitals. Researchers can look for associations between rotating night shift work and cancer.


These researchers conclude “long-term rotating night-shift work was associated with a higher risk of breast cancer, particularly among women who performed shift work during young adulthood.”


These researchers found that the “risk for rectal cancer significantly increased with shift work duration, suggesting that long-term circadian disruption may play a role in rectal cancer development.”


Breast and colon cancer were the 2nd and 3rd leading causes of cancer related deaths in women in 2017.


Sleep deprivation effects on other diseases


There are many other studies linking poor sleep to poor health outcomes. This includes obesity, diabetes, and metabolic syndrome. Sleep also affects your immune system. You are more prone to getting a viral infection if you have insufficient sleep.


Poor sleep even affects your genes. Chronic sleep deprivation causes changes to genes involved in oxidative stress and metabolism. Researchers have even linked short sleep duration to biomarkers of aging.


How to go to sleep faster?


Every physician wants to help support sleep. But medical schools and residencies provide inadequate training. Physicians end up utilizing the few tools in their toolbox to address insomnia. Many of these tools are medications. You may have heard of some of these medications -- ambien, lunesta, sonata, ativan, xanax.


Many patients self medicate. They find that alcohol helps them fall asleep. But when you look at what alcohol does to our brains, alcohol is more a sedative than a sleeping aid. It’s like getting anesthesia rather than getting restorative sleep.


Sleep stages, REM sleep, NREM sleep


There are two types of sleep. There is rapid eye movement (REM) sleep and non rapid eye movement (NREM) sleep. REM and NREM sleep each have its own special brainwave findings. We cycle through REM and NREM sleep many times throughout the night. The time we spend in each stage of sleep is critical to how we function.


Alcohol effects on sleep stages


Alcohol suppresses REM sleep in the first part of the night. It then lengthens it in the second part of the night. This results in fragmentation of sleep. The quality of sleep after you drink alcohol decreases.


In fact, there are many studies looking at the importance of the time spent in REM and NREM sleep. We need to spend enough time in each stage of sleep. Fragmenting the stages of sleep harms many aspects of our lives. These include the ability to form memories, concentrate, and learn.


Know the risks with sleep aids


There are issues with sleeping medications. These medications usually fall into the hypnotics drug classification. Side effects include daytime sedation, drowsiness, dizziness, lightheadedness, cognitive impairment, and motor impairment. Hypnotics can worsen underlying sleep disorders. Hypoventilation syndrome as well as obstructive sleep apnea get worse after taking hypnotics. Many of these medications are also habit forming. Sudden cessation causes rebound insomnia. This is a condition where your insomnia becomes worse than what it was before. Those are the well known side effects. The less known side effects are much worse.


These researchers performed a meta analysis of almost 9000 subjects. These subjects were randomized to one of four hypnotic medications. Eszopicolone, ramelteon, zaleplon, and zolpidem. There was another group of 4400 controls without medications. The medication group had increased risk for upper respiratory infections and pneumonia.


Several observational studies have found an association between hypnotic drugs and mortality. These researchers looked into this in greater detail. They found that receiving hypnotic prescriptions was “associated with greater than threefold increased hazards of death even when prescribed <18 pills/year. This association held in separate analyses for several commonly used hypnotics and for newer shorter-acting drugs.”


Subanalysis revealed that there is a dose response association for mortality. Taking up to 18 doses per year increased your risk by 3.6 times. Taking between 18-132 doses per year increased your risk by 4.43 times. Taking greater than 132 doses per year increased your risk by 5.32 times. Frequent use also increased risk for cancer by 1.35 times.


Cognitive behavior therapy for insomnia


The American College of Physicians released a practice guideline for treating insomnia. They suggest all adults should receive cognitive behavioral therapy for insomnia (CBT-I) as the initial treatment. Trained therapists help patients build upon sleep hygiene principles. They help individualize methods for patients and solve patient specific barriers. More and more institutions are providing electronic or virtual cognitive behavior therapy.


There are also free apps available. CBT-i Coach is a free app developed by the Department of Veterans Affairs in collaboration with Stanford University. There are many other paid apps focusing on CBT-i as well. Many of these principles can also be found at the national sleep foundation website.


What to do about insomnia? Check your sleep hygiene


Here are some sleep hygiene principles to put in place in no particular order of importance.


Limit your exposure to light near bedtime.


These researchers found that “compared with dim light, exposure to room light before bedtime suppressed melatonin, resulting in a later melatonin onset in 99.0% of individuals and shortening melatonin duration by about 90 min.”


Melatonin plays an important role in the circadian rhythm. Our bodies produce melatonin right after sunset. The higher the levels of melatonin, the more sleepy we will feel. Light suppresses melatonin. In fact, just 8-10 lux of light can delay melatonin release. For reference, a typical living room may have around 50 lux of light.


Moreover, the suppression of melatonin is most sensitive to short wavelength light (ie. blue light). Electronic devices all emit blue light. This will affect our ability to sleep. Try to limit electronic devices close to bedtime.


Keep the bedroom cool.


Have you noticed it’s easier to fall asleep in a cool bedroom than a warm one? This is because our core temperature decreases while we are asleep. If we are in a warm bedroom, our bodies need to work extra hard to lower our core temperature. A cool bedroom will help our body lower its core temperature. 65 degrees Fahrenheit seems to be ideal for most people.


Try taking a warm shower or bath before bedtime.


These researchers found that a warm shower or bath before bedtime can improve your sleep. It can help with how fast you fall asleep. It can increase your total sleep time and sleep efficiency. It can improve how well rested you feel after your sleep. This has to do with core temperature. A warm shower or bath before bedtime will dilate the blood vessels in your extremities. Vasodilation helps to radiate heat from your body. This in turn lowers your core temperature.


Evaluate your room.


Get rid of loud sounds that disturb sleep. If you can’t, try ear plugs or white noise machines. Smart phones have lots of free apps that can substitute for a white noise machine.


Make your room free of light. Blackout curtains or eye shades are great options.


How to fix your sleep schedule? Stick to a routine.


Humans are creatures of habit. Falling asleep is no different. Create a schedule that makes sense for you and stick to it. This includes weekdays, weekends, holidays, and vacations. Stick to your schedule. Find something relaxing to do before bedtime. Avoid anything that will cause excitement, stress, or anxiety.


Exercise daily.


Many studies agree that daily exercise is a great treatment for insomnia. These researchers showed that moderate intensity exercise had “reduction in the sleep onset latency (55%) and in the total wake time (30%); increase in total sleep time (18%), and in the sleep efficiency (13%).”


Try not to exercise 2 hours before bedtime. Strenuous exercise will increase your core temperature. A higher core temperature makes it more difficult to fall asleep.


Only go to bed if you are sleepy.


Get out of bed if you are not asleep within 20 minutes. Go into another dimly lit room and do something relaxing until you feel tired. Your bed should only be used for two activities. One of them is sleep.


Things to avoid.


Avoid alcohol as this affects the quality of your sleep.

Avoid stimulants such as nicotine or caffeine.

Avoid heavy meals in the evening. A light snack is better than going to bed with a full stomach.

Avoid a full bladder. Reduce fluid intake after dinner to avoid needing to get up to use the toilet.

Avoid having a clock facing your bed. This removes any anxiety behind watching the clock.


Prioritizing sleep may be one of the most important things you can do for your health. If you are suffering from sleep problems, talk to your doctor about how you can prioritize your sleep.


© 2020 by Jeffrey Peng MD