Sleep
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The Sleep Cycle & The Role of Each Sleep Stage
We hope that every member of Benchmark gains an understanding of the importance of sleep. Sleep is the FOUNDATION of our health. The other pillars of health - exercise, nutrition and emotional connection - are grounded in sleep. Sleep is a biological necessity and helps every single part of our body function. It is referred to as ‘Mother Nature’s Elixir’ and we are going to teach you why.
What is sleep?
Sleep is a period of rest for the body and mind. We have different sleep stages that are grouped into “REM” (Rapid Eye Movement) and non-REM, or “NREM.” NREM is further categorized into NREM stages 1 through 4, which represent progressively deeper phases of sleep.
As you move into deeper sleep, your heart rate slows, your body temperature drops and your brain waves slow down. During our Deep NREM sleep (stages 3 and 4), our body restores itself. It repairs tissues, builds bones and muscles, and strengthens the immune system. This type of sleep also helps us regulate various hormones including cortisol, insulin, leptin, and our growth hormone. Deep NREM sleep helps to weed out and remove unnecessary neural connections. It also moves short term memories into more permanent long-term storage.
Our sleep will always progress through our Non-REM sleep in stages 1 through 4 which lasts approximately 70 minutes. We then move to lighter sleep, from NREM stage 4 to 3 and then to 2 and then into REM sleep.
REM sleep is characterized by rapid eye movements, muscle paralysis and irregular breathing. Our brain waves during REM are similar to what they are when we’re awake. It is during REM that we experience dreaming. Muscle paralysis of our voluntary muscles (not breathing or heart muscles) protects us from acting out violently in our dreams and injuring ourselves or others. This type of sleep is crucial for emotional regulation and memory consolidation. Dr. Matthew Walker, sleep expert, has referred to REM as your “emotional first aid”. REM helps process emotions and takes the visceral reaction out so that we can wake up the next morning and feel better about a situation or event. I can definitely relate to this and always follow my mom’s advice “sleep on it, you will feel better in the morning” and I always do, thanks to my REM sleep.
REM is also crucial for our memory consolidation. After NREM sleep weeds out the unnecessary memories and preserves the important ones, REM sleep solidify neural connections for enhanced learning and integration.
Our NREM sleep helps us store the information we’ve gathered while awake. It keeps what is important and stores it in a safe place. Our REM sleep then integrates this information. REM helps us gain insight and problem solve.
Our sleep cycle takes about 90-120 minutes. Cycling in the first half of the night is mostly deep NREM sleep and the second half is more REM sleep. This natural cycle of sleep can be dangerous for early risers because waking up 1-2 hours earlier could lose the majority of your REM sleep.
Sleep’s Impact on Your Health
Sleep & Heart Health
Sleeping protects your heart. Sleep deprivation causes chronic activation of the autonomic nervous system, in particular our fight or flight response known as sympathetic nervous system. Chronic activation of this system causes greater levels of adrenaline and cortisol (stress hormones) which cause elevated blood pressure and higher heart rates. Higher levels of cortisol can cause metabolic dysfunction as well. In addition, sleep deprivation will inhibit the release of growth hormone which heals the body. Growth hormone replenishes the lining of our blood vessels. Without growth hormone, our blood vessels become thickened and not as elastic which can cause even higher blood pressure.
When we sleep well, deep NREM sleep helps the brain communicate a calming signal to our nervous system which promotes the activation of our parasympathetic nervous system (the rest and digest system). Our parasympathetic nervous system lowers heart rate, helps to dilate our blood vessels and reduces our blood pressure. Deep NREM sleep can be seen as a natural form of blood pressure medication.
Sleep & Metabolism
Sleep deprivation affects our metabolic health. When we are sleep deprived, we see a rise in blood glucose and insulin resistance. Literature shows a clear association between poor sleep and the risk of developing type 2 diabetes. It is interesting to hear from our members who experience a bad night of sleep while they are wearing their continuous glucose monitor. Their blood glucose readings on the CGM when they rise are higher than they are after a good night’s sleep.
In addition to poor sleep causing elevated levels of blood glucose, it also causes weight gain. We have two prominent hunger hormones called leptin and ghrelin. Leptin’s job is to signal to the body a sense of feeling full. Ghrelin, on the other hand, triggers a strong sensation of hunger. Studies have shown that when individuals are sleep deprived, their leptin levels decrease and their ghrelin levels increase. This is a double whammy. Lower levels of leptin decrease our body's feeling of being full and higher levels of ghrelin increase our sensation of hunger which causes sleep deprived individuals to want to eat more food. Studies show that individuals who are sleeping less will consume on average 300 more calories per day than well rested individuals. This can easily result in 10-15 pounds of weight gain over a year.
Referenced studies:
Van Cauter E, Spiegel K, Tasali E, Leproult R. Metabolic consequences of sleep and sleep loss. Sleep Med. 2008 Sep
Kristen L. Knutson, Karine Spiegel, Plamen Penev, Eve Van Cauter, The metabolic consequences of sleep deprivation, Sleep Medicine Reviews, Volume 11, Issue 3, 2007.
Sleep & Immunity
Healthy sleep helps to strengthen the functioning of our immune system. One disrupted night of sleep causes a reduction in our natural killer cells. Natural killer cells are produced by our immune system and target foreign and abnormal cells in our body, including cancer cells. If we sleep less than 4 hours a night, we will see a 70% reduction in our natural T cells until the next sleep cycle. This reduction puts us at risk for catching infection and for not targeting dangerous cells.
Studies have also found that our sleep impacts our response to the standard flu vaccine. A group of healthy adults were separated into two groups - one group had their sleep restricted to 4 hours a night for 6 nights and the other group was allowed 7.5 to 8.5 hours a night for sleep. At the end of the six days, everyone was given a flu shot. The group that had 4 hours of sleep had a 50 percent immune reaction compared to the group of participants who slept more than 7 hours.
Sleep & Brain Health
Sleep is crucial for our brains. We have already discussed that our NREM sleep helps us strengthen our new memories by keeping what is important and storing it in a safe place. Our REM sleep integrates this information. REM helps us gain insight and problem solve. Sleep therefore helps us learn new information and apply it.
Sleep also helps the brain practice motor skills in the absence of any further practice. Sleep helps the brain to automate the movement routines of a certain skill, making them more effortless.
The other fascinating aspect of sleep is a nighttime power cleanse that occurs during deep NREM sleep. Our brains have a glymphatic system that uses cerebrospinal fluid to bathe the brain and help collect and remove dangerous metabolic contaminants generated by the neurons in our brain. Proteins that are removed during this process include amyloid protein and tau protein which are two proteins found in patients with Alzheimer’s disease. Amlyoid build up further exacerbates the problem because amlyoid tends to build up in the areas of the brain that are needed to generate deep sleep. More amyloid, less deep sleep, less deep sleep, more amyloid, and so on. Sadly, getting too little sleep in your adult life will significantly raise your risk of developing Alzheimer’s disease.
Sleep & Fertility
Poor sleep in men leads to decreased levels of testosterone. In fact, a group of young healthy men in their mid-twenties were limited to five hours of sleep a night for one week and researchers found a marked drop in their baseline levels of testosterone. Men who report sleeping too little not only have decreased levels of testosterone but their sperm counts are lower and the sperm themselves have more deformities than those men who are obtaining a full and restful night of sleep.
Lower testosterone not only has an effect on fertility but it also affects (among other things) energy, mood, focus, muscular mass, bone density and libido.
Women experience reproductive issues with poor sleep as well. Women who routinely sleep less than 6 hours a night experience a 20% drop in follicular releasing hormone which is a hormone that helps the ovary prepare eggs for ovulation. Women who are shift workers will often experience irregular menstrual cycles. As a result, 80% of women who work erratic hours were found to have issues with fertility.
How We Measure Sleep & How to Improve It
How do we measure sleep?
For your Benchmark, you will wear a wearable for 4 weeks, which among other things, tracks your sleep. We measure sleep duration, restorative sleep (deep sleep + REM), and sleep consistency. We track sleep for 4 weeks, and offer advice based on your personal data.
How can you improve your sleep?
A few strategies can be very impactful:
Figure out your rhythm. Everyone has a different circadian rhythm and figuring out what your rhythm is will help you abide by it. This rhythm is also not a choice, it is mostly genetically determined, and referred to as a “chronotype.” There are 22 genes that affect your sleep chronotype. The chronotypes are: (extreme morning (ideal sleep time of 8pm-4am), morning (9:30 to 5:30/6), neutral (11 to 7:30), evening (12:30am to 9:30), extreme evening (2:30am to 11:30am). The Chronotype MEQ (morningness eveningness questionnaire), takes 3-4 minutes and will give you an idea of where you fall. Society is heavily biased toward morning types, which can be difficult for those of us who aren’t naturally early risers. Once you know the ideal time for your body to sleep, you can do a few other things to help you set your circadian rhythm, so you can sleep better….
Light exposure: Exposing yourself to light in the morning sets off your circadian rhythm. We want as much light exposure as we can throughout the day and ideally this is natural light. At night we want to reduce our light exposure. Darkness stimulates the hormone melatonin which triggers the body that it is time to go to sleep. 3-4 hours we should start to think about reducing lights and especially within 1 hour before bed. Blue light from screens reduces melatonin and forces it to peak later in the night. One study compared those reading iPads vs those reading books before bed. iPad readers had 20% less melatonin, and melatonin peaked 3 hours later, resulting in less REM and these participants felt less refreshed. To help get to sleep and stay asleep, keep the room very dark. Take advantage of eye masks, night hoods, or black-out blinds, and remove or cover light emitted by electronics.
Stay cool - Dropping our core body temperature will help us fall asleep and stay asleep. Try to cool your body temperature before going to bed. You can do this by taking a hot shower, putting socks on your feet, or taking a sauna. Counterintuitively, this helps heat leave your body through your extremities, which cools your core body temperature. It is also important to keep your body temperature cool throughout the night. Keep your room at 65 deg F or 18 deg celsius for optimal sleep.
Exercise helps with quality sleep. Expending energy during the day will help improve your sleep. There is conflicting evidence around the best timing of exercise to optimize sleep, but it’s clear that it’s best to avoid exercise within an hour of bedtime.
Be mindful of the timing of your food & drinks. Caffeine blocks adenosine which is a chemical that makes you sleepy. So caffeine will keep you feeling alert. Try to stop caffeine by noon. Caffeine has a half life is 5-7 hours - meaning 50% of caffeine concentration will be in the bloodstream which causes fragmented poor sleep. Try to eat your last meal of the day 3 hours before bed. Eating right before bed can cause indigestion and can raise your core body temperature. Try to limit your alcohol intake because alcohol is a sedative. It will give you fragmented sleep and reduce your REM sleep. If you do have alcohol, try to have this 3-4 hours before you go to bed and drink plenty of water.
Maintain consistent timing. Try to keep your sleep as consistent as possible. Go to bed and wake up within a 30-minute window each day to achieve your highest-quality sleep.
Additional Content Recommendations
For a deeper dive on this topic, we recommend:
📚 Why We Sleep, by Matthew Walker (Amazon.ca / Amazon.com)