The importance of sleep
“Sleep is the elixir of life. It is the most widely available and democratic powerful healthcare system I could ever possibly imagine.” – Dr Matthew Walker (Sleep Expert and Neuroscientist)
The impact of sleep on human health and disease is an interesting topic that is revealing to be more important than we once understood. We all know the value of sleeping well and waking up refreshed, and on the other hand, we have all experienced the feeling of fatigue after a poor night’s sleep. But even though we know this, in our busy society, many of us are still not getting the quality sleep needed to truly receive the health benefits of sleep.
So, just how much, or how little sleep is considered not enough? Matthew Walker, Professor of Neuroscience and Psychology at Berkeley University defines not enough sleep as less than 7 hours on a consistent basis. Yep, you read that right, less than 7 hours!
Research by the Sleep Health Foundation found Australian’s average reported sleep time is 6 hours and 43 minutes, although 12% of the population sleep less than 5 and a half hours and only 8% over 9 hours. And if you think you’re someone that can perform on less than 7 hours of sleep on a consistent basis, you would have to be in the small fraction of <1% of the population who has a certain mutation in the gene DEC2 that allows you to survive on 5 hours of sleep. Great if you are! But, you’re probably not. You are more likely just getting by and not performing anywhere near your optimum capability. Many people walk through their lives in an under slept state, not realising it. It’s become this new natural base line. It’s a little bit like the drunk driver at a bar who has had a couple of shots and some beer, and they say, well, “I’m perfectly fine to drive home”. And you say, no, I know that you think you’re fine to drive, but trust me. Objectively, you’re not. And the same is true for sleep.
Let’s look at the implications current research suggests from not getting enough sleep:
One study showed a 60% increase in probability of injury comparing people who get 9 hours of sleep a night, to those who get 5.
The less sleep you get, the lower your peak muscular strength, lower your vertical jump height, and lower your peak running speed.
If you’re getting 6 hours of sleep or less, your time to physical exhaustion drops by up to 30%.
Lactic acid builds up quicker the less you sleep. This causes fatigue in your muscles and a burning feeling. It can also cause nausea and weakness.
Studies show shorter sleep predicts all caused mortality. This means death from all causes.
Men who sleep 5-6 hours a night will have a level of testosterone 6-10 years their senior.
Insufficient sleep is the most significant lifestyle factor for determining whether or not you’ll develop Alzheimer’s Disease.
People sleeping 4-5 hours a night will on average eat 200-300 extra calories each day (this equates to 70,000 extra calories each year, which translates into 4-8KGs of extra body mass).
Drowsy driving kills more people on the roads than alcohol or drugs combined. When you’re under slept, you have micro sleeps, in which the eyelid partially closes, but the brain goes to sleep for a brief period of time.
One study sleep deprived individuals for one night (to 4 hours of sleep) – they experienced a 70% reduction in critical anti cancer fighting cells (natural killer cells).
Sleeping less than seven hours per night itself has been associated with either having diabetes or eventually developing the condition.
It’s no wonder health professionals are advocating sufficient sleep as “the greatest legal performance enhancing drug that most people are probably neglecting”.
Let’s look at the different stages of sleep
During sleep, the body moves through five different stages of both REM (rapid eye movement) and non-REM (non-rapid eye movement) sleep. Over the course of the night, the body will spends an average of 90 minutes in each stage and go through this five-stage cycle four to six times.
Each stage of sleep serves a unique restorative function, including muscle recovery, hormone regulation, clearance of toxins from the brain, and memory consolidation, making it essential to allow enough time to cycle through all sleep stages. Without a full night of sleep, your body and mind are deprived of the essential elements needed to help you conquer the day.
Stage 1
Stage one of sleep, also known as the transitional period between wakefulness and sleep, occurs when one finds themselves floating in and out of consciousness. During this non-REM stage, you may be partially awake while your mind begins to drift off.
This period of drowsiness eventually leads to a light sleep and slips you into stage two.
Stage 2
Over the course of the night you spend almost 50% of the time asleep in stage two. Stage two is also a non-REM phase and is one of the lighter stages of sleep. During this stage, the heart rate begins to slow and the core body temperature decreases. Eye movement stops and brain waves slow with the occasional burst of waves called sleep spindles.
Stages 3 & 4
Stages three and four are often grouped together because they are the periods of slow wave sleep (SWS). Stages three and four are characterised as the deep stages of sleep, and are often the hardest to wake up from. If you try to wake someone up when they are in stages three or four, they will most likely be disoriented and groggy for minutes after they awake.
Slow wave sleep is the deepest sleep that your body enters throughout the night and is a non-REM phase of sleep. It is called slow wave sleep because the brain waves slow to what are known as delta waves with the occasional faster wave. As the body moves from stage three to stage four, the number of delta waves increase and the faster waves decrease.
In addition to the deep sleep caused by the delta waves, blood pressure drops even further, and breathing becomes deeper, slower, and more rhythmic. There is no eye movement during slow wave sleep, and the body becomes immobile.
However, the muscles still have the ability to function, even though there is no muscle movement. These are the stages when children sometimes experience nightmares, bedwetting and sleepwalking.
Stages three and four of sleep are extremely regenerating to the body. During slow wave sleep, hormones are released that aid in both growth and appetite control. The growth hormones help to replenish muscles and tissues that were exerted over the course of the day, and the appetite controlling hormones help limit feelings of excessive hunger the following day.
These hormones are essential to the development of a strong body and help control unnecessary over-eating. In addition to the release of critical hormones, the blood flow to the muscles increases, providing restorative oxygen and nutrients.
Stage 5
Stage five is the only stage of rapid eye movement (REM), and is unlike any other sleep phase because the brain is exploding with activity. Most adults spend about 20% of sleep in REM, while infants spend almost 50%. During non-REM sleep, the mind rests while the body heals, but in REM sleep the mind energises itself while the body is immobile.
REM sleep is called as such because the eyes dart in various directions while the limbs and muscles are temporarily paralysed. Breathing becomes shallower and irregular while the heart rate and blood pressure rise from the levels they were in previous stages.
Most dreaming takes place in stage five as a result of heightened, desynchronised brain waves, almost similar to being awake. This stage of sleep rejuvenates the brain, supporting sharp and alert daytime function.
Individuals begin waking up at the end of stage 5. Upon waking up, an individual’s core body temperature begins to rise in order to prepare the body for the activity of the day ahead.
Let’s look at the important role each stage of sleep plays in our health
Sleep cleans your brain
The body has a sewage system that you may have heard of “the lymphatic system”, but only recently did we discover that the brain has one too. During deep sleep at night, there is a sewage system in the brain that cleanses the brain of all the metabolic toxins that have accumulated throughout the day called the glymphatic system. During sleep, the space in the cavities of the glymphatic system increase by more than 60%, allowing a “flushing” operation to take place and effectively eliminate potentially neurotoxic waste products. One of those toxins is beta amyloid – which is responsible for the underlying mechanism of Alzheimer’s disease. The less you sleep – the more this plaque builds up. In a study conducted by the American Neurological Association, adults who were subjected to sleep deprivation for 36 hours, experienced a 50% increase in a protein called tau that is linked to neuronal cell death and Alzheimer’s disease.
Sleep facilitates information storage
Long-term memories are formed via transfer from the hippocampus to the brain’s cortex during sleep, where they can be retrieved for future use. If the transfer phase doesn’t take place, we run the risk of a problem readily observed in older adults who experience loss of slow wave sleep and subsequently demonstrate difficulty retaining memories overnight called hippocampal-associated memory impairment.
Sleep that occurs after learning new information, acts as the “save button”. Think of the information you learn throughout the day as documents that need to be filed into a filing cabinet. While you’re sleeping, the filing process is taking place. If you get the recommended 7-9 hours sleep, your filing is done efficiently and without errors. If you get, say 5 hours sleep, files will get missed or things will be filed incorrectly. It’s like your boss forcing you to do 9 hours of work in only 5 hours, you will undoubtably make a few mistakes and a few things will get missed.
Sleep preps the brain for information input
The formation, or “encoding” of memories occurs when the brain engages with new information – ideas, actions, or images – and leads to the formation of a representation of this information in the brain. Sleep preps the brain so that it can assimilate this new information and lay down the framework for new memory traces. Without sufficient sleep – in particular, the slow wave sleep that occurs during the stage of non-rapid eye movement, or NREM – the brain’s ability to receive new input is markedly impaired. This phenomenon has critical implications in students and has been observed when college students who were deprived of sleep experienced dramatic deficits in their ability to learn new information. Studies suggest as much as a 40% reduction in the ability to retain a learned word list in people who are sleep-deprived.
Sleep recharges your heart and cardiovascular system for the next day
One large study found that getting 5 or fewer hours of sleep per night was associated with a 45% increase in the risk of heart attack (the researchers controlled for age, weight, smoking, and snoring). This is believed to be due to the benefits lost from your heart rate slowing dramatically during deep sleep.
Screen time, darkness, melatonin and sleep
One hour of iPhone, TV or laptop use before bed will delay the onset of melatonin production by about 3 hours, your peak melatonin levels will also be about 50% less. Melatonin is a hormone that plays a vital role in regulating the sleep cycle, and is released when darkness begins. During the day, melatonin is suppressed and only very low levels can be detected in the brain and body.
Caffeine and sleep
Caffeine is the second most traded commodity on the surface of the planet after oil. That’s a lot of sleepy people using caffeine to get by! The quarter-life of caffeine is 12 hours. So if you drink a coffee at noon, at midnight a quarter of that caffeine is still in your brain. Only somewhere between 24 and 36 hours after consuming caffeine will it have completely left your system.
Darkness, light and sleep
It may seem obvious that darkness plays in instrumental role in our sleep quality, however, what you may not realise, is light is just as important. Because sleep operates around our circadian rhythm (link) which is controlled mostly by our environment including light and dark exposure, it is vital to get the right amount of exposure to both. In order to produce melatonin (also known as the sleep hormone), it is essential to have complete darkness. Of course, these days, we spend far too much time exposed to bright lights on our phones, laptops and T.Vs, especially too close to bed time, when in fact, what we should be doing is dimming the lights and avoiding technology as we wind down for bed. Even as much as a small amount of light from your alarm clock can reduce the production of melatonin and therefor make it difficult for you to fall asleep and stay asleep. First thing in the morning it is recommended that you get 20 minutes of sunlight exposure to again produce the right hormones for your circadian rhythm, in this instance, we want a spike in cortisol so we can jump out of bed and get on with the day.
Tips for getting better sleep
Go to bed and wake up at the same time every day, even after a bad night’s sleep or on the weekend. I know this sounds tuff and unrealistic, but do this majority of the time and you will see the impact.
Keep your bedroom temperature cool; about 65 degrees Fahrenheit is optimal for cooling your body towards sleep. Wear socks if your feet are cold.
An hour before bedtime, dim the lights and turn off all screens. Blackout curtains are helpful.
Establish a regular, relaxing bedtime routine. Such as taking a bath or listening to music, brushing your teeth and washing your face in the same way every night.
Keep the bed for sex and sleep only. If you can’t sleep, get out of bed and do something quiet and relaxing until the urge to sleep returns. Then go back to bed. The brain is such an associative device that it will very quickly build a connection between the bed and wakefulness if you stay awake in bed.
Avoid caffeine after 1 p.m. and never go to bed tipsy. Alcohol is a sedative and sedation is not sleep. It also blocks your REM dream sleep, an important part of the sleep cycle.
Try meditating: it quiets the mind, and it dampens down the fight-or-flight branch of the nervous system (sympathetic nervous system), which is one of the key features of insomnia.
Supplement with melatonin. Melatonin's main job in the body is to regulate night and day cycles or sleep-wake cycles. Supplementation is generally regarded as safe and can help if needed.
Try to avoid prescription drugs. The benzos are addictive and can cause rebound insomnia once you go off them. And if you must take them, try to only take them very sparingly because of the addictive nature of them.
If you can’t sleep. Get out of bed and do something quiet and relaxing until the urge to sleep returns. Then go back to bed.