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Sleep is like hunger or thirst, there is a drive for it – you get tired, so you sleep. In fact, did you know that humans spend approximately one third of their entire lives asleep? But the reason or purpose behind why we sleep is still very mysterious with many unanswered questions. Nevertheless, what we do know is that sleep is a crucial pillar of health, with various research suggesting that it plays an important role in memory consolidation, hormone regulation and tissue repair in the body. Yet, when it comes to maintaining a healthy lifestyle sleep seems to be an element that is often forgotten or receives less focus. This can be detrimental to one’s health as poor sleep or lack of sleep can have many negative effects on the mind and body, including increasing the risk of cardiovascular disease, diabetes, obesity, and depression. It also makes it harder to concentrate, exercise, decreases reaction time and performance, and can alter one’s mood and perception significantly.

Unfortunately, these issues do not seem to be the number one thing on our minds right before bed when you want to watch just one more episode of your favourite show or read one more chapter of an engrossing book. It becomes easy to push off bedtime and say I’ll catch up on missed sleep on the weekend. However, repaying your slept debt on the weekends or any other catch up day for that matter does not work. Although that extra sleep may lessen daytime sleepiness for the time being, it throws off your internal biological clock, also known as your circadian rhythm. 

If you are a night shift worker or frequent subject to jet lag, not disrupting your natural circadian rhythm is often hard to avoid. When your circadian rhythm is out of sync it means your internal biological clock is mismatched with the actual clock. As a result, your sleep-wake cycle is interrupted, making it harder to either fall asleep or stay awake.

 

STAGES OF SLEEP

There are two different states of sleep; non-rapid eye movement sleep (NREM or non-REM) and rapid eye movement (REM) sleep. Within NREM sleep we also have three stages of sleep; stage 1, stage 2, and stage 3. Throughout the night you will cycle through all sleep stages multiple times, with the average sleep cycle lasting from 90 to 120 minutes. The longer you sleep, the more sleep cycles you will have. However, in one sleep cycle each sleep stage is not split up equally. For example, in the earlier portion of the night there is more stage 3, in comparison to the later portion of the night or early morning where REM sleep is longer.

 

Stage 1

Stage 1 NREM sleep is first stage of sleep we enter after wakefulness. It normally only lasts several minutes and is the lightest sleep stage and therefore one can be easily awoken from this state. During this stage your brain waves start to slow, transitioning from alpha waves (which occur during wakefulness) to theta waves. In turn, your breathing and heartrate slow down, your muscles begin to relax, and eyes start to roll.

 

Stage 2

Stage 2 NREM sleep is the lighter stage of sleep before deep sleep. During this stage your body temperature drops, eye movements begin to stop, and brain waves slow to theta waves. But the distinct characteristics of this sleep stage are the short bursts of electrical activity called spindles, and K-complexes which often occur in response to external stimuli such as noises in your bedroom.

 

Stage 3

Stage 3 NREM sleep is a deep stage of sleep where your breathing and heartrate has slowed to its lowest point. It is also referred to as Slow Wave Sleep (SWS) because during this stage your brain waves are at its slowest. These waves are called delta waves. A person is often difficult to arouse or awaken in this deep stage of sleep. 

 

REM:

REM sleep is the stage when dreaming occurs and is easily distinguished by its sharp rapid eye movements. It is also characterised by a suppression of muscle tone, where your arms and leg muscles become temporarily paralysed which is believed to stop you from acting out your dreams. During this sleep stage your brain wave activity presents in the form of theta waves or ‘saw tooth’ waves. Your breathing also becomes faster and your heartrate increases. When awoken in this sleep stage most people will feel groggy and still tired as they have woken up from a very deep stage of sleep.

  

SLEEP DISORDERS

Most people have experienced troubles sleeping at least once or twice in their life, but when this becomes a regular occurrence you should consider the possibility that you are suffering from a sleep disorder. There are many types of sleep disorders but here is breakdown of the most commonly seen:

 

Sleep Disordered Breathing (SDB)

SDB is term used to describe a group of disorders where the partial or complete cessation of breathing occurs involuntarily during sleep. Many know this as sleep apnoea. There are three types of sleep apnoea; Obstructive Sleep Apnoea (OSA), Central Sleep Apnoea (CSA), and Mixed/Complex Sleep Apnoea.

 

Narcolepsy

To be narcoleptic means to have excessive and uncontrollable daytime sleepiness. There are two forms of narcolepsy; narcolepsy without cataplexy and narcolepsy with cataplexy. Cataplexy is the sudden loss of muscle control when you are awake, often triggered by strong emotions such as laughter or anger. An evident marker for narcolepsy is when a person enters REM stage sleep (our deepest stage of sleep) immediately after sleep onset.

 

Insomnia

Insomnia is a sleep disorder where a person finds it difficult to fall asleep and stay asleep throughout the night. There is a number of possible causes such as: jet lag, poor sleep habits, stress, health conditions, medications and more. However, in many cases the cause is unknown or not as obvious. 

 

Parasomnia

Parasomnia describes a group of sleep disorders that cause abnormal and unwanted behaviours when falling asleep, during sleep, or when waking up. There are many types of parasomnias, some of the most recognised are; Sleep walking, Sleep Eating Disorder, sleep talking, bruxism (teeth grinding), REM Behaviour Disorder, night terrors, and more.  People often have no memory of these experiences or events occurring.

 

Restless Legs Syndrome (RLS)

RLS is a neurologic sensorimotor disorder that causes an uncontrollable urge to move your legs when you are resting or lying down. The urge to kick or twitch your legs typically comes from trying to rid the legs of an uncomfortable, aching and tingling sensation. The symptoms are typically most severe at night whilst sleeping.

  

TIPS TO IMPROVE YOUR SLEEP

Although there are many sleep disorders that could explain having poor sleep or lack of sleep, sometimes all it comes down to is good sleep hygiene. In sleep medicine, sleep hygiene refers to your bed habits before you go to sleep. One of the biggest mistakes people make is turning their place of sleep, into a place of wakefulness. It becomes very easy to fall into the habit of watching TV or sitting on your laptop or phone scrolling through social media in the comfort of your bed before you go to sleep. However, each of these activities occurs when you are awake and you are performing them in a place of sleep. When this repeatedly happens your body starts to recognise your bed not as a place of sleep, but rather a place of wakefulness, ultimately making it harder for you to shut your mind off and go to sleep. This is why it is encouraged to not lie in bed awake, if you cannot sleep it is best to get out of bed and do something until you feel tired, such as reading a book in a chair or listening to music. But it is not just your night time routine that is important, but also your morning routine. In order to assist the circadian rhythm, the best thing to do when you first wake up is to get outside and into the sunlight.

 

Here are some other helpful tips to help improve your overall sleep:

  • Create a routine - try to go to bed and wake up at the same time everyday
  • Allow at least an 8 hour window for sleep time
  • Avoid caffeine and alcohol late in the day or before bed
  • Limit screen time before bed
  • Exercise for 30 minutes a day, but not too close to bedtime
  • Ensure your bedroom is dark, quiet and cool in temperature

 

In a Nutshell

It's time to put some care and effort into that one-third of your life you spend asleep. With so many important physiological functions occur during your sleep, you have an amazing opportunity to transform your health by making some basic changes. It takes time to shift your sleep quality, be patient, focus on your sleep hygeine and start putting those beneficial bed habits in place.

 

Author: Sophie Hastie 

Sophie Hastie is a Clinical Measurements Scientist in Sleep and Respiratory Medicine.

 

REFERENCES

  1. Kryger, M.H., Roth, T., & Dement, W.C. (2011). Principles and Practice of Sleep Medicine. 5th edn. United States: W.B. Saunders.
  2. org. (2020) Available at: https://www.sleepfoundation.org (Accessed: 27 February 2020).
  3. National Institute of Neurological Disorders and Stroke (2019) Brain Basics: Understanding Sleep.Available at: https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep(Accessed: 29 February 2020).
  4. Sleep Health foundation. (2020) Available at: https://www.sleephealthfoundation.org.au (Accessed: 29 February 2020).

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