Numerous functions of the brain are restored and deepened by sleep. Whether your primary objective in life is to become the leading sales rep for a global company, improving your talent in a competitive sport, losing a few pounds of fat, or maintaining your cognitive and physical functions into old age, substantial sleep is not only recommended but essential.
Without adequate sleep (seven to nine hours each night), your future will undoubtedly consist of working longer hours at the office to make up for a lack of productivity, increased injuries and/or illnesses resulting in the inability to truly reach your highest potential both inside and outside of the gym and/or office and inevitably, a shorter, less enjoyable lifespan.
As Matthew Walker says,
“The shorter you sleep, the shorter your life span. The old maxim: ‘I'll sleep when I'm dead’ is therefore unfortunate. Adopt this mindset, and you’ll be dead sooner and the quality of that (shorter) life will be worse.”
Although this may come off as a bit overly dramatic, it is the truth, and thanks to Matthew Walker’s passion on sleep research and his new book, Why We Sleep, this information is now becoming more apparent than ever before. This article will talk about eight (out of the very many) reasons why we sleep. For more information regarding sleep, sleep medication, ways to enhance your sleep and so much more, I would highly suggest getting a copy of this book. The information below is derived directly from Matthew Walker’s book, Why We Sleep, and is only the tip of the iceberg.
Memory and Learning
Each of the three types of sleep, including REM (rapid eye movement) sleep, stage 1 NREM (non rapid eye movement) sleep, stage 2 NREM sleep, and slow wave sleep all have various and extremely important functions throughout the night. Many of these functions are integral to memory, learning and consolidation. The first benefit of sleep in regards to memory and learning is the transfer of short-term, fact-based memories into long-term storage within the brain. This is an important component before learning as it frees up necessary space in order to make new memories.
The hippocampus provides a place to store short-term information but is extremely limited. During stage 2 NREM sleep, this information is transferred to the cortex, which is responsible for long-term memory storage. This is done through pulses, known as sleep spindles, which travel between the hippocampus and the cortex, thus freeing up space to take on new short- term information the following day.
As Walker found in his sleep research: “The pulses kept weaving a path back and forth between the hippocampus, with its short- term, limited storage space, and the far longer storage site of the cortex (analogous to a large memory hard drive). In that moment we had just become privy to an electrical transaction occurring in the quiet secrecy of sleep: one that was shifting fact-based memories from the temporary storage depot (the hippocampus) to a long-term secure vault (the cortex).”
The second benefit in regards to memory comes after learning and takes place during deep NREM. There was such a strong correlation between the amount of deep sleep an individual received the night after learning new information that Matthew Walker could predict just how much information the participant would remember the following morning. Studies also show that those who follow learning with eight hours of sleep versus eight hours of wakefulness have a memory retention gain of 20-40 percent. A great excuse to discontinue the dreaded all- nighters before a big exam or company presentation.
Spring Cleaning For Your Brain
“The two most feared diseases throughout developed nations are dementia and cancer. Both are related to inadequate sleep.” - Matthew Walker
Alzheimer's disease is associated with the buildup of a toxic protein known as beta-amyloid. Amyloid plaques are poisonous to neurons and are responsible for killing surrounding brain cells. They are also known for attacking the regions of the brain responsible for producing quality deep sleep, which as discussed above, is crucial for memory and learning. Studies done by Dr. Matthew Walker and Dr. William Jagust at the University of Berkeley found that those with higher levels of plaque build-up had the most severe loss of deep sleep and therefore had failed to successfully consolidate new memories.
A more important piece to the Alzheimer puzzle emerged when Dr. Maiken Nedergaard at the University of Rochester discovered the glymphatic system within the brain. This system is responsible for collecting and removing dangerous metabolic contaminants through cerebrospinal fluid that bathes the brain during sleep. The glymphatic system is effective in flushing out metabolic debris during deep sleep because the glial cells of the brain shrink up to 60 percent, enlarging the space around the neurons for proper cleansing. Therefore, inadequate deep sleep results in a missed opportunity to clear beta-amyloid from the brain, thus making it more difficult over time to produce the quality deep sleep needed in order to receive the necessary spring cleaning for your brain each night.
“From this cascade comes a prediction: getting too little sleep across the adult life span will significantly raise your risk of developing Alzheimer's disease.”
It’s no coincidence that when you fall victim to an illness like the flu, you also find yourself with a complete lack of energy resulting in more sleep than usual. This is because there is a strong association between your immune system and sleep!
“Sleep fights against infection and sickness by deploying all manner of weaponry within your immune arsenal, so much so that even one night of poor sleep increases your risk of illness significantly.”
A study conducted by Dr. Aric Prather at the University of California found a clear, linear relationship between sleep and infection. In summary, the less sleep an individual was getting a week before they were given a dose of the rhinovirus virus, the more likely it was that they would be infected and catch a cold. The study found that those sleeping five hours on average, had a 50 percent increased risk in developing the flu, whereas those sleeping seven hours or more the week prior, had an infection rate of just 18 percent.
Another important role of the immune system are Natural Killer cells, which are responsible for clearing out foreign elements such as malignant tumor cells. One night of poor sleep was shown to decrease the natural killer cells circulating the immune system by 70 percent, compared to a full eight hours of sleep. Another massive reason why adequate sleep is so important for our health and immune system!
Have you ever felt extremely irritable after a night of poor sleep? You are not alone! The amygdala, located in the left and right side of the brain, is responsible for triggering strong emotions and has been shown to be 60% hyperactive in underslept individuals.
“It was as though without sleep, our brain reverts to a primitive pattern of uncontrolled reactivity.”
Inversely, the prefrontal cortex, a region of the brain most developed in humans, which is known for rational, logical decision making and thought processing had a strong connection to the amygdala. With adequate sleep the two work together beautifully by providing a regulatory balance between the erratic emotional gas pedal of the “fight or flight” amygdala and the emotional regulation brake of the prefrontal cortex. As you probably guessed, with little sleep the amygdala becomes hyperactive while the prefrontal cortex loses its rational ability. This results in irrational thoughts and behavior. There is now evolving evidence in adolescents identifying a link between sleep disruption and aggression and bullying across all ages as well as an increase in suicidal thoughts, attempts and completion in the days after little sleep.
In summary, sleep is an essential component in regulating emotional stability and health in both adults and adolescents.
Blood Sugar Management
If you have a history of high blood sugar, diabetes, or a specific goal of losing fat for personal or health reasons, sleep is just as important (if not more so) as nutrition. When you search the internet for fat-loss protocols, you’ll see thousands of results on the perfect “diet” or workout routine to shed fat fast; but what you won’t see is the role sleep plays in managing blood sugar, an essential component for fat loss.
“Sleeping less than seven or eight hours a night will increase your probability of gaining weight, being overweight or being obese, and significantly increases your likelihood of developing type 2 diabetes.”
In the simplest of terms, insulin is secreted from the pancreas when glucose levels are elevated in the bloodstream. This can result from numerous causes such as a rise in cortisol from stress and exercise to carbohydrate intake. Insulin’s role is to send signals to the cells to absorb glucose from the blood in order to be used as energy within the body. But, when the body becomes less receptive to insulin, also known as insulin resistance, the cells struggle to get the memo, leaving blood glucose levels high and causing more insulin to be secreted from the pancreas.
Scientists have found that just one night of poor sleep caused the cells to repel, rather than absorb, high glucose levels from the blood.
“Chronic sleep deprivation is now recognized as one of the major contributors to the escalation of type 2 diabetes throughout first-world countries.”
Sleep is not only necessary in managing blood sugar but is also an important component in regulating appetite.
Not only does inadequate sleep cause your body to be less resilient to insulin and high blood sugar, it also causes more intense cravings for the types of food that elevate your blood glucose levels in the first place. A catch 22 if you will.
Sleep loss increases levels of endocannabinoids, which stimulate appetite and increase your desire to snack and even impacts various hormones responsible for controlling appetite. Leptin signals are necessary for creating a sense of satiation whereas ghrelin triggers a strong sensation of hunger. When levels of ghrelin increase, so to does your appetite. Studies done by Dr. Eve Van Cauter at the University of Chicago found that those who slept less than five hours a night had decreased concentrations of the satiety-signaling hormone and increased levels of the hunger- initiating hormone. This caused more tendencies not only to overeat but also to overeat foods higher in refined carbohydrates.
“A sleep-deprived body will cry famine in the midst of plenty.”
If you’re looking to enhance your performance in the gym, reproduce successfully or even keep up with your appearance, vitality and well-being, you will surely benefit from adequate sleep.
Scientists took a group of healthy, young males and decreased their sleep to five hours a night for an entire week. They took hormone samples before the study began to create a baseline while they rested and again after the study was completed. Researchers found a significant drop in testosterone relative to their initial levels.
“The size of the hormon- blunting effect was so large that it effectively ‘aged’ a man by ten to fifteen years in terms of testosterone virility.”
As for women, routinely sleeping less than six hours a night has been shown to decrease the follicular-releasing hormone, a critical reproductive element crucial for ovulation, by 20 percent.
“Reproductive hormones, reproductive organs, and the very nature of physical attractiveness that has a say in reproductive opportunities: all are degraded by short sleeping.”
Did you know that each year, you and many others have been a part of a global experiment on the effect of sleep and cardiovascular health? Neither did I, until recently! This experiment is also known as Daylight Savings Time. Year after year there is an inverse relationship between sleep and heart attack rates the day after we shift our clocks. When the clock springs forward in March resulting in a one-hour loss of sleep, heart attacks spike. Meanwhile in the fall, when we push our clocks back, resulting in a one-hour increase of sleep, heart attacks decline.
Why is there a strong correlation between inadequate sleep and cardiovascular health?
During NREM sleep, the brain communicates a relaxing signal to the sympathetic nervous system, also known as the fight-or-flight portion of the autonomic nervous system. Therefore, deep sleep has an important function in regulating physiological stress known to increase blood pressure, heart attack and stroke.
Deep sleep is also essential for growth-hormone secretion, which is necessary not only for building lean muscle mass and recovery after training but also for replenishing the lining of your blood vessels, also known as endothelium. Without growth hormone, this lining will become slowly stripped of their integrity.
“Think of deep NREM sleep as a natural form of nighttime blood-pressure management —one that averts hypertension and stroke.”
Surviving on Little Sleep?
Many people THINK they are immune to the negative effects of poor sleep because they FEEL perfectly fine throughout the day after short sleep. Unfortunately that is most likely NOT the case! Individuals who truly believe their cognitive function and health are intact after chronic sleep deprivation (anything under seven hours of sleep) fail even the simplest of cognitive and memory consolidation tests and suffer the same ill effects of little sleep.
However, there is a very rare collection of individuals who can survive, and survive well, on six hours of sleep per night relative to the recommended eight hours. This is partly due to genetics, specifically a sub-variant of a gene called BHLHE41, also known as DEC2. Scientists are still trying to understand the effects and how it is correlated to sleep resilience.
“The number of people who can survive on five hours of sleep or less without any impairment, expressed as a percent of the population, and rounded to a whole number is zero.”
So unfortunately, it is better to play it safe and continue focusing on increasing your sleep quality and quantity of sleep to ensure you are resilient, productive and healthy enough to reap the benefits of your hard work later in life.
Stay tuned for an upcoming article on a few ways you can enhance your sleep but in the meantime, sleep well, my friends!