Updated: Jan 28
Sleep is essential to all organisms. Every animal requires sleep to a degree, though sleep behaviour is slightly different in some animals such as dolphins, which can have half of their brain asleep at a time (we have all felt that way sometimes) while the other side remains alert and conscious. (1) This evolved mechanism helps dolphins and other cetaceans avoid predators whilst they sleep. What do dolphins have to do with how long you should sleep? Not much really. We just thought it was interesting! The fact remains that we all need sleep. Sleep deprivation can ultimately lead to a rather serious condition called “death” which goes a way to demonstrate the importance of sleep.
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What Happens When You Sleep?
Sleep can be characterised by a state of altered consciousness, inhibition of sensory and muscular activity and reduced interaction with surroundings. We sleep in cycles of R.E.M. and non-R.E.M. sleep (R.E.M. stands for rapid eye movement).
R.E.M. sleep is a “lighter” phase of sleep where the majority of dreaming occurs due to brain activity increasing which leads to the phenomena which gives R.E.M. sleep its name, rapid eye movement. During this phase, muscles become paralysed, possibly to stop us acting out our vivid dreams, and fluctuations in homeostatic mechanisms occur. Roughly 20-25% of total sleep time is spent in R.E.M. sleep.
Non-R.E.M. sleep can be split into 3 stages, ingeniously named stage 1, stage 2 and stage 3. (Up until 2008 non-R.E.M. sleep was split into 4 stages until the American Association of Sleep Medicine combined stages 3 and 4 into a single stage).
You are closest to being awake. If you were to wake in this stage of sleep, you might not realise you’ve been sleeping. Short naps fall into this category. You are also likely to experience hypnagogic jerks, where you feel you are falling and suddenly awaken. No-one is quite sure why this is, but one hypothesis suggests it is “an archaic reflex to the brain's misinterpretation of muscle relaxation with the onset of sleep as a signal that a sleeping primate is falling out of a tree. The reflex may also have had selective value by having the sleeper readjust or review his or her sleeping position in a nest or on a branch in order to assure that a fall did not occur”,(2) but not enough evidence exists to prove this. This stage of sleep normally only lasts around 10 minutes and makes up for about 5% of total sleep time.You are closest to being awake. If you were to wake in this stage of sleep, you might not realise you’ve been sleeping. Short naps fall into this category. You are also likely to experience hypnagogic jerks, where you feel you are falling and suddenly awaken.
The transitional and preparatory stage of sleep where we get ready for a phase of deep sleep. We become harder to awaken, muscles begin to relax and conscious awareness of surroundings decreases. As we pass through this phase multiple times throughout the night when transitioning to and from stage 3 sleep, it constitutes approximately 45-55% of total sleep time.
Also known as “slow wave” sleep, this is the most “restful” of sleep stages and is essential to a restful nights sleep. In this stage of sleep the body is in a mainly anabolic state where essential skeletal, neural and muscular repair takes place. This occurs as a result of a decrease in sympathetic nervous system (“fight or flight”) activity and an increase in parasympathetic nervous system (“rest and digest” or “feed and breed”) activity. Growth hormone - one of the bodies main anabolic hormones - is sporadically released in this period. This phase of sleep is also important for generation of memory and as a means to recover from a days activities. This phase of sleep constitutes 15-25% total sleep.
A typical nights sleep follows a pattern of non-R.E.M. sleep followed by R.E.M. sleep. Non-R.E.M. sleep consists of transitioning from stage 1 - stage 2 - stage 3 - stage 2. From stage 2 we transition into R.E.M sleep where we remain for 10-25 minutes. The cycle of non-R.E.M. and R.E.M. sleep continues throughout the night with periods of stage 3 sleep shortening and possibly disappearing, and stages of R.E.M. sleep lengthening as the night goes on. Most of the slow wave sleep we experience occurs within the first 4-5 hours of sleep.
Benefits Of Sleep
Sleep is vital to human life. We do not yet know everything there is to know about sleep. It remains one of life’s mysteries. What we do know is that sleep facilitates a multitude of important functions and provides benefits such as:
- Brain Function
Sleeping allows the brain to rest and repair. One good night of sleep can improve your ability to learn new motor skills by 20% and eight hours of sleep can increase the brain’s ability to process complex tasks by 50%. (3)
- Hormone Optimisation
- Beauty Sleep
Yep, it is true. We all need our beauty sleep. A good nights sleep has been shown to promote skin health and a youthful appearance. Who hasn't been frightened by their own reflection after a bad nights sleep? (7)
- Athletic Performance
Optimal testosterone levels are important for athletic performance. Sleep allows muscles to repair and new tissue to form. Reduced rates of injuries and improved reaction times are other benefits associated with sleep. (8)
Whatever non-medical ailment you are suffering from, chances are they stem from inadequate sleep. Mental fog, being fat, lack of motivation, weakness or depression. These can all be attributed to not sleeping enough and fixed with a decent nights sleep.
Check out this great infographic to find out more about the benefits of sleep.
This begs the question “how much sleep should we be getting?”. The general consensus is 7-9 hours per night, but the real answer is dependent on a few things (nothing is ever straight-forward):
- Activity Levels
Active people should aim to get 8-10 hours of sleep. If you are an active person, have an active job, exercise frequently or generally spend a lot of time on your feet, then you will need more sleep per night. The body needs to recover from the physical stress of the day and sleep facilitates these reparitive processes. (9)
There are many parents who have bemoaned their teenage child for sleeping until the early hours of the afternoon, but these long periods of sleep are vital to proper growth and development. Babies pretty much only eat and sleep (ahh, the good life) and older children still need up to 8 -10 hours of sleep. At this crucial point of life, allow nature to take its course where possible and sleep as much as needed. (10)
- Fighting Infection
There exists a bidirectional communication link between the central nervous system and peripheral immune system. As a result of neuro-immune communications, sleep patterns alter immune function and immune challenges require extra sleep. This explains why we feel lethargic when we are ill or sense the onset of an infection. If you are fighting an infection or have a taxed immune system you should aim to sleep for longer. (11)(12)
- Sleep More Than Five Hours
5 hours is the minimum amount of sleep we should get. A study of 38,000 people under the age of 65 showed an increase in risk of mortality in 65% of cases. As previously mentioned, we get most of our slow wave sleep in the first 4-5 hours of sleep. Always aim to get at least 5 hours of sleep and if you regularly under-sleep aim to make up for it where possible. Which leads us on to the next point… (13)
- Sleep Debt
The short term negative effects of sleep deprivation can be reversed by ensuring you get two or more consecutive night sleep of 7-9 hours. In the study mentioned above, those who had longer periods of sleep at the weekend showed no increased risk of mortality. If you build up a sleep debt, repay it! (14)
- Too Much Is Not Better
If you find yourself regularly sleeping more than 9-10 hours a night without a clear cause (exercise, stress, heat fatigue) and wake up feeling inadequately rested then it could be a symptom of an underlying medical issue. Consult your medical practitioner or a functional medicine doctor.
- Sleep In A Pitch-Black Room
Our bedrooms are brighter than we think. From LEDs emitting low-level light, to poor quality blinds letting in light from the street outside, our bedrooms are not dark enough to have a proper nights sleep. When light is sensed, (and yes, you can sense it through your eyelids) the pineal gland releases less melatonin - the hormone crucial for sleep. Invest in black-out blinds and cover all light sources in your room. (15)
- Cold Room
Our core temperature drops by 1-2 degrees as we fall asleep. Temperature regulation is important to sleep quality - ever notice how in the summer it is hard to fall asleep on a hot, stuffy night? Ensure your bedroom is cool enough for your body temperature to drop and facilitate a good night sleep. (16)
- Don’t Eat Too Close To Bedtime
Aim to finish eating around 3 hours prior to going to bed. This could mean eating your last meal at 7pm to be in bed by 10pm. Eating too close to sleep can lead to indigestion so if you must eat before bed, aim to eat something easy to digest. An omelette with spinach is a good option as they both contain good levels of tryptophan which aids sleep. (17)(18)
- Develop Consistent Sleep & Waking Times
Go to sleep and wake up at the same times each day; this way the body develops a rhythm which enables it to work more efficiently. Excluding babies, children and teenagers, aiming to go to sleep at 10pm and wake up at 6am everyday, including weekends, will create a stronger foundation for important and demanding processes such as digestion, respiration, movement etc to be performed. When the body's circadian rhythm is disrupted by a change in time-zone or irregular sleep and waking times, all of the body's systems become dysfunctional which is why it is common to experience a drop in energy levels among many other symptoms.
For more tips on a better bedtime routine check out our article.
Be conscious of your sleep quality and sleeping patterns to ensure you get adequate rest. If you sleep for only 5-6 hours per night on a regular basis, you should aim to make up for it where possible. It may be a good idea to track your sleep using a sleep log.
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ABOUT THE AUTHORS
John Maitland is the co-founder of 'The Evolved Way.’ A personal trainer with over 10 years’ experience, he has worked alongside a wide range of leading CEOs, entrepreneurs and medical professionals. John is a keen athlete and holds a black belt in Shaolin Kung fu. A fan of the great outdoors, he can often be found exploring the British countryside and mountains...or breaking pine boards with his fingers.
Co-founder of 'The Evolved Way', and experienced personal trainer, Samson practices what he preaches. His own healthy lifestyle, which informs this site, is based on understanding the right way to eat and exercise, not excluding of course going out and enjoying life knowing you can still feel and look good.