In this entry, we’ll introduce some surprising connections between sleep and vital body functions. We tend to vastly underappreciate the contribution sleep makes to our overall health. If we feel tired, we drink some coffee. Because we no longer feel tired, we don’t realize that our bodies are still functioning under the compromised health that accompanies deprivation. This deficiency manifests in both physical and psychological ways. Further, when we feel we don’t have enough time in our days, rather than cutting back on commitments to allow proper rest time, we often wake up earlier or “burn the midnight oil” to compensate for our busy lifestyles. In truth, we should be sleeping through one-third of our lives.
Often, we don’t realize how important sleep is for our bodies’ vital (life-preserving) functions. However, within every metric we use to assess our health, the only common denominator in one way or another is rest. It should seem more obvious when we consider that our bodies are made to shut off on their own if we neglect this necessity. Unfortunately, this mechanism can lead to other problems, ranging from students falling asleep in class to drivers passing out at the wheel and causing a fatal car accident (consequently, many doctors and scientists are now equating driving while sleep-deprived with driving under the influence of alcohol[i]). So, in considering the body’s natural mechanism that mandates slumber even when we don’t wish to prioritize it, that may come as a small surprise. Studies show that going two or three weeks without sleep, could be fatal.[ii] More practically speaking, a study released in 2009 by Dr. Thomas Roth, director of research for sleep disorders at the Henry Ford Health System, stated that “chronic sleep restriction is associated with…a deterioration of daytime performance, including memory, and a number of physiologic consequences, including adverse effects on endocrine functions and immune responses and an increase in the risk of obesity and diabetes.”[iii] Sleep deprivation has also been correlated to type 2 diabetes, heart disease, obesity, and even premature death amongst the elderly.[iv]
Grab Some Coffee?
Some think that the only bad effect of sleep deprivation is waking up tired. So, they believe creating a habit of morning caffeine intake equals problem solved.
No drowsiness, no problem—right?
Many don’t realize that caffeine is a way of tricking your body into muting signals sent by something called adenosine—also referred to as “sleep pressure.”[v] This is the substance that builds up within the brain during waking hours in order to induce sleep at the right times of the evening, and ensuring that sleep will last long enough to produce healing and restoration for the body and mind.
Caffeine, on the other hand, silences the signals sent by adenosine, kicking in about a half hour after consumption and staying in the system for between five to seven hours.[vi] Thus, in addition to the damage done by lack of sleep because caffeine tricks us into thinking that we’re not tired, caffeine gives us the added damage of adenosine being unable to lull us into slumber when it’s finally time to sleep if we drink it too late in the day, as many do. The University of California at Berkeley’s professor of neuroscience, Matthew Walker, stated that caffeine is “the most widely used (and abused) psychoactive stimulant in the world…[constituting] one of the longest and largest unsupervised drug studies ever conducted on the human race.”[vii]
During our waking hours, as stated previously, adenosine mounts within the brain—hence the phrase “sleep pressure”—until we rest and the pressure is relieved. We must achieve adequate amounts of this inactivity in order to remove all the mounted pressure, which builds in proportion to our waking hours. Sleep pressure carries over, meaning that long-term deprivation is accompanied by a continual, lingering amount of adenosine. This unrelieved burden feeds long-term sleepiness and fatigue, and even takes an overall toll on cognitive functions. While caffeine may temporarily alleviate the symptoms of the mounting adenosine, the sensation of sleep pressure will return as the caffeine wears off. There is only one way to be completely rid of this mounting compression: getting the proper amount of good-quality slumber.[viii]
Unfortunately, many of us go about our days stifling the signal receptors of adenosine and “running on coffee.” In doing so, we sell ourselves—and our health—short. This is often because we take sleep for granted, presuming that our brains are inactive while we sleep since we don’t remember doing anything. However, nothing could be farther from the truth. In actuality, our brains are extremely busy while we sleep, conducting and overseeing an array of vital functions, without which our physical and psychological health are compromised.
Unfortunately, this is added to the before-mentioned fact that many are using technology too late in the day, allowing screen light to throw off their circadian rhythm and adversely impacting sleep routines. This further compromises our health via lack of quality and quantity of sleep. In fact, the National Sleep Foundation states that 90 percent of Americans regularly subject themselves to excessive screen time.[ix] This negatively alters the structure of patterns that have evolved over the ages, exposing us to durations of light known by no previous generation.
Sleep Phases or Cycles
In beginning our study of sleep, we need to understand what the ideal night looks like and what cycles it includes. The ordinary sensory perceptions we notice during waking hours still surround us; our bodies can still feel, smell, and even taste while we’re asleep. However, these signals don’t usually pull us from slumber because the thalamus (the part of the brain that regulates signals of sensation) shuts off these triggers while we’re asleep. The thalamus acts as a “gatekeeper,” deciding which signals are worth interrupting sleep for and which to disregard.[x] As the body slips into sleep, there are multiple phases of sleep that we need to experience for quality rest. If the sleep cycle is interrupted or the body can’t reach the full depth of each cycle, the brain is unable to complete the cycles of healing and detoxification that need to take place. Opinions vary as to how many phases take place in sleep. Some say the number is three: NREM (non-rapid eye movement), slow wave sleep, and REM (rapid eye movement). Others break down the stages further, rendering up to five. I, myself (Daniel), believe there are four: two phases of NREM, slow wave, and REM. Regardless, the operations that take place during sleep and their vitality remain the same. The entire sleep cycle lasts approximately ninety minutes and restarts throughout the night after each full rotation. Let’s look at an example of a four-sleep-cycle model listed below:
NREM 1: The person has fallen into a light sleep. He or she is easily roused from this state, and if awakened, may be unable to tell whether sleep was achieved at all. This usually lasts only fifteen to twenty minutes.
NREM 2: The body is preparing for deep sleep. Muscles contract and unwind, but slowly settle into deeper relaxation as the body temperature decreases and the heart rate slows. This lasts approximately fifteen minutes.
Slow-wave sleep: This is sometimes also known as NREM 3. During this time, the brain is conducting metabolic, healing, and detox functions and effectively moving the previous day’s memories into long-term memory storage. Muscle tissue is rejuvenated, the immune system is restored, and 95 percent of the daily supply of growth hormones is produced.[xi] This can last up to an hour at a time.
REM: This phase usually lasts the final ten minutes of the sleep cycle. This is the when dreams take place, causing the eyes to move about under closed eyelids. REM concludes the sleep cycle, meaning that the full rotation of ninety-minute rest has been achieved. At this point, the body often stirs lightly and then reenters NREM1, restarting the succession. Ideally, we will experience four completed sequences each night for optimum health.
You might be thinking that human growth hormone is of no concern since you are a full-grown adult. However, while actual growth is part of “growth hormone’s” appropriate context where children are concerned, the term also covers a vast array of processes that have nothing to do with reaching the physical adult size. These hormones stimulate “bone growth, immune function, amino acid uptake, protein synthesis and muscle glucose uptake,” induce the “burning of fat from adipose tissues,” and play a “key role in maintaining cardiovascular health.”[xii]
In other words, these are very important to the body’s health. Thus, the deprivation of sleep that contributes to decline exacerbates health problems that stem from these systems reacting adversely through such responses as a weakened immune system, inefficient burning of fat, diminished muscle mass and performance, and increased signs of aging, such as thinning skin resulting in wrinkles.
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When most people think about certain lifestyle factors that affect insulin sensitivity and blood glucose levels, they think about nutrition, calories, fasting, or exercise. Sleep usually doesn’t enter the conversation, because we rarely understand how vital sleep is to our blood sugar and glucose management. However, studies have shown a significant link between sleep deprivation and insulin sensitivity. Further, multiple nights of too little sleep can have negative long-term effects, including insulin resistance and impaired glucose tolerance. As a result, long-term sleep deprivation can lead to metabolic illness or conditions such as diabetes.
During slow-wave sleep, the growth hormone is produced and the nervous system’s activity decreases. Additionally, the production of cortisol (a chemical that causes alertness and is often produced as a byproduct of stress) minimizes, which allows the brain to operate using less glucose, restoring glucose/insulin balance to the system.[xiii]
A lack of slow-wave sleep is related to such conditions as type 2 diabetes and other insulin-related illnesses. One study involved sleep disturbances that weren’t intrusive enough to wake the participants, but were enough to keep them from lapsing into slow-wave sleep. After regularly practicing this for a series of nights, the participants were found to have 25 percent lower glucose tolerance (the body’s ability to successfully process glucose) than before the experiment began. Another study showed that otherwise healthy people who were restricted to four to six hours of sleep each night for less than a week, like those in the previously mentioned study, marked a glucose tolerance that was lowered by an average of 40 percent, “reaching levels that are typical of older adults at risk for diabetes, which is characterized by high glucose levels due to insufficient insulin.”[xiv] Further, when participants were fed breakfast, their glucose levels remained higher than their pre-experimental state, confirming the connection between glucose intolerance and sleep deprivation.[xv] Lack of adequate rest has also been found to manifest in chronic stressing of the entire body, which contributes to elevated blood sugar as well, expounding the problem.[xvi]
In preparation for the morning, the body begins to secrete hormones that help us wake. This usually occurs between 3 and 4 a.m. The secreted hormones include growth hormones and cortisol, along with elevated blood sugar. These are the brain’s way of preparing the body for a day of alertness and manual labor, but can result in overly heightened blood sugar upon waking for those who struggle with insulin imbalance, glucose tolerance, or diabetes.[xvii]
Snoring and Sleep Apnea
Unfortunately for those who have trouble getting a good night’s rest due to snoring or sleep apnea, allowing the issue to go unaddressed can result in “developing certain types of metabolic syndrome(s); including diabetes, obesity, and high blood pressure. This likelihood…increased dramatically to 80% in those who found it difficult to fall asleep and to 70% for those who woke up not feeling as refreshed.”[xviii] This is because those who chronically snore or suffer sleep apnea may have trouble reaching the deepest states of sleep, and thus are deprived of the “insulin reset” that takes place during slow-wave sleep. As an added frustration, chronic sleep deprivation can throw off blood sugar levels, causing them to elevate, which interferes with the body’s ability to sleep. This creates a perpetuating cycle—and likewise elevates the risk of diabetes.[xix]
Sleep disturbances can cause the overproduction of cortisol. Since this anti-inflammatory agent is the brain’s response to stress, a little of it is beneficial. As stated earlier, some of this hormone is released in anticipation of waking up, to help us approach the incoming day with alertness. However, an overabundance (triggered by a brain that keeps waking throughout the night, as if in “false-start” motion) leads to obesity, reduced glucose tolerance, a weakened muscular and skeletal system, potentially high blood pressure, and worse, loss of cognitive function.[xx]
Frequent Urination and Thirst
High blood sugar causes the kidneys to over-function, causing individuals to wake up many times throughout the night to urinate. This can be because the body is working too hard to expel elevated levels of sugar in the blood stream. Unfortunately, this can be another self-perpetuating issue, as interrupted sleep feeds chronic sleep deprivation, which in turn increases glucose levels. In response, the body craves water to support the continual urination, triggering more sleep disruptions and excess fluids that the body will attempt to expel. Again, the cycle can continue if not addressed.[xxi]
Ghrelin is a hormone that triggers the “hungry” mechanism in our brain. Leptin—its partner in crime—dispatches in tandem with it, often sending out a sensation similar to panic to our brains, convincing us that we are starving. Unfortunately, sleep deprivation causes production of ghrelin to increase by as much as 15 percent, causing our hunger to spike. Leptin is thrown completely out of balance, adding an urgency to the hunger that is felt by the sleep-deprived snacker. Simultaneously, metabolism slows alongside the fat-burning mechanism, causing the body to consume more calories and store more fat than it is able to burn in a day. The cycle can lead to obesity; those who get less than four hours of rest habitually increase their odds of becoming obese by 73 percent.[xxii]
Because of the strong correlations between hypertension, high blood pressure, diabetes, heart attack, stroke, and obesity, it seems obvious that cardiovascular health is greatly affected by our sleeping habits. But recently, studies are confirming a direct link between “preclinical atherosclerosis [hardening of arteries as a byproduct of plaque] and…a higher rate of death among patients with heart disease.”[xxiii] Dr. Arshed Quyyumi, director of the Emory Clinical Cardiovascular Research Institute, oversaw the analysis of data from more than 2,800 coronary artery disease patients revealing that nearly 80 percent of those studied had an increased risk of mortality and simultaneously slept either under or above the recommended timeframe for nightly rest.[xxiv] Factoring in variables, the doctor concluded that there was “almost a 40 to 50% increased risk of dying if you are sleeping too little or too much.”[xxv]
Atherosclerosis, as mentioned before, is plaque buildup in arteries that, over time, causes them to harden. In one study, experimenters segregated two groups of mice and treated them just the same, other than keeping one group awake while the others were allowed ample sleep. The rest-deprived mice underwent a plummet in their levels of hypocretin—a hormone in the hypothalamus that promotes the “awake” feelings enjoyed by those who practice healthy sleeping habits. Similarly, in patients who have sleep disorders such as narcolepsy, hypocretin is unusually low. The decreasing presence of this substance in the mice caused the body to respond with a spike in a protein known as CSF1, which “increased production of inflammatory white blood cells in the bone marrow and accelerated atherosclerosis.”[xxvi] Conversely, when hypocretin levels were again balanced within the mice, the atherosclerosis process immobilized.[xxvii]
Because atherosclerosis can lead to stroke, hypertension, heart attack, and coronary artery disease, and can affect nearly all the major organs of the body, this imbalance of hormones can be a dire, even deadly, threat. This is just one more way that regular sleep helps regulate the balance of hormones and other body chemicals and keeps inflammation—and many chronic illnesses—at bay.
UP NEXT—SLEEP AS SUPER-POWER PART 2: Cognitive Function and Emotional Well-being
[i] Eugene, Andy & Masiak, Josh. “The Neuroprotective Aspects of Sleep.” US National Library of Medicine. November 18, 2015. Retrieved March 4, 2020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4651462/.
[ii] Roth, Thomas. “Slow Wave Sleep: Does It Matter?” US National Library of Medicine. April 15, 2009. Retrieved March 4, 2020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2824210/.
[iv] “Restoring Deep, Slow Wave Sleep to Enhance Health and Increase Lifespan.” Nutrition Review. July 5, 2014. Retrieved March 4, 2020. https://nutritionreview.org/2014/07/restoring-slow-wave-sleep-shown-enhance-health-increase-lifespan/.
[v] Walker, Matthew. Why We Sleep: Unlocking the Power of Sleep and Dreams. (New York: Simon & Schuster), Pg. 27–28.
[viii] Ibid., Pg. 28–30.
[ix] “Why Electronics May Stimulate You Before Bed.” Sleep Foundation Online. Retrieved march 4, 2020. https://www.sleepfoundation.org/articles/why-electronics-may-stimulate-you-bed.
[x] Walker, Why We Sleep, Pg. 40.
[xi] “Understanding Sleep Cycles and the Stages of Sleep.” Whoop Online. November 1, 2019. Retrieved March 4, 2020. https://www.whoop.com/the-locker/understanding-the-stages-of-sleep-how-to-optimize-it-with-whoop/.
[xii] “Restoring Deep, Slow Wave Sleep,” Nutrition Review. Retrieved March 4, 2020.
[xiii] “Sleep Longer to Lower Blood Glucose Levels.” Sleep Foundation Online. Retrieved March 4, 2020. https://www.sleepfoundation.org/excessive-sleepiness/health-impact/sleep-longer-lower-blood-glucose-levels.
[xvi] Hines, Jennifer. “Blood Sugar and Sleep Problems: How Blood Sugar Levels Impact Sleep.” Alaska Sleep Education Center Online. August 7, 2018. Retrieved March 4, 2020. https://www.alaskasleep.com/blog/blood-sugar-and-sleep-problems.
[xx] “Restoring Deep, Slow Wave Sleep,”Nutrition Review. Retrieved March 4, 2020.
[xxi] Hines, “Blood Sugar and Sleep Problems,” Retrieved March 4, 2020.
[xxii] “Restoring Deep, Slow Wave Sleep,” Nutrition Review. = Retrieved March 4, 2020.
[xxiii] Kuehn, Bridget. “Sleep Duration Linked to Cardiovascular Disease.” AHA Journals Online. May 20, 2019. Retrieved March 5, 2020. https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.119.041278.
[xxvi] Rettner, Rachel. “Here’s How Poor Sleep May Hurt Your Heart.” Live Science Online. February 13, 2019. Retrieved March 5, 2020. https://www.livescience.com/64761-sleep-heart-disease.html.