Understanding Sleep

Sleep Patterns

Sleep is basically separated into Rapid Eye Movement (REM) sleep and Non-Rapid Eye Movement (NREM) sleep. The purpose of NREM sleep is body restoration while that of the REM sleep is brain restoration by strengthening, refreshing and organizing memory (Campbell, 2002[9] and Robson, 2008[12]). NREM sleep is further divided into four stages from the lightest to the deepest (Caldwell, 2006[8]).

NREM sleep - Stage 1

  • the transition phase between wakefulness and sleep
  • takes 10 minutes each time
  • the brain activity, eye movement and muscle activity become slower
  • where some people may notice a feeling of falling which is caused by the sudden contraction of the muscles
  • a person is easily awoken
  • waking up in this stage of sleep will cause a person to feel that he/she has not slept.

NREM Sleep - Stage 2

  • light sleep
  • first stage of true sleep
  • lasts from 10-25 minutes each time
  • occupies 50% of the sleep patterns
  • the brain activity, eye movement become even slower and the cardiac activity decreases

NREM Sleep - Stage 3

  • the beginning of deep sleep
  • slow-wave delta sleep
  • the brain activity and eye movement are approaching to zero
  • if a person is awoken in this stage of sleep, he/she may feel groggy or disorientated for a few minutes.

NREM Sleep - Stage 4

  • deep sleep
  • slow-wave delta sleep
  • no eye movement or muscle activity
  • if a person is awoken in this stage of sleep, he/she may feel groggy or disorientated for a few minutes.

REM sleep

  • known as paradoxical sleep
  • usually occurs 70-90 minutes into a sleep
  • happens in cycles lasting for approximately 10 minutes initially to 1 hour
  • the eyes move rapidly from side to side and the brain waveform is similar to that when a person is awake
  • where the dreams occurs
  • As we grow older, the time spent in REM sleep declines from 50% of our sleep for infants, to 20% of our sleep for adults.

The diagram above indicates brainwave activity during the different stages of sleep. As we can see, the wavelength is greatly increased during deep sleep as compared to the other stages. Therefore, for a person to be woken up during a deep sleep, it will take some time for reorientation to return to a relaxed/waking brainwave pattern.


(Figure Adopted from (De Landra, 2003))

As shown in the above figure, the four stages of NREM sleep and the REM sleep progress cyclically in an average of 90 to 110 minutes with a longer REM sleep and lesser deep sleep time as the cycle succeed (Campbell, 2002 and Sleepdae, n.d.).

The Homeostatic Component of Sleep

The Homeostatic Component depicts the need for sleep in relation to being awake and being asleep. It tells us that the longer that we are awake, the higher the pressure it is for us to need sleep. The Homeostatic mechanism regulates the sleep intensity. Meaning that the higher the pressure, the greater the intensity will be of the sleep.


The graph on the right shows that the need to sleep increases when we are awake and decreases rapidly when we are sleeping. If we however increase the amount of time we sleep, our sleep cycle gets shorter with our need to sleep becoming lesser.

We may think that it is a good thing to have more sleep and shorter sleep cycles since our body will be well rested. However, the opposite is true. Deep sleep is directly proportionate to the intensity of our need to fall asleep. As the pressure/need to sleep decreases, the amount of deep sleep we receive dissipates. Therefore, we often feel lethargic and tired when we sleep too much due to our bodies not being able to regenerate itself with the lack of deep sleep.

The Circadian Cycle


Many of us are familiar with the Circadian Cycle. It represents our level of alertness throughout the day. It takes into account, biological elements such as our body temperatures, heart rate and blood pressure.


These elements affect the our level of alertness during the course of a day. It is affected by our daily activities such as mealtimes, exercise and level of stress. The graphs above shows the normal results of an average person during a normal day. These elements co-relate and when put together, plots our the Circadian Rhythm with which our level of alertness is affected.

As we sleep, our heart rate is lowered and hence as seen on the graph, our level of alertness is reduced. Other things that may reduce our level of alertness also includes that of our blood pressure which is often lowered after meal times.

As pilots flying across different time zones through the night, we are not able to fully apply the Circadian Cycle without understanding or adjusting it. By understanding how our alertness is affected by our blood pressure, heart rate and body temperature, we can then make adjustments to our diet and sleep to ensure a safe level of alertness in the cockpit.

Sleep Deprivation


The graph above shows three different sleeping patterns. The blue line depicts the normal sleep pattern while the red line depicts a person awake for 40 hours and lastly the green line depicts a person who takes a 2 hour nap during the day.

As we can see, our need to sleep increases as our time awake increases. The intensity of the need to sleep increases with the lack of sleep as seen in the red graph. However, the amount of time required for recovery during the time asleep remains the same or similar in all the three scenarios. The only difference is the intensity in which the recovery takes place. Hence, from the graph, we can see that a sleep deprived person will undergo a longer period of deep sleep in his/her 8 hours to ensure sufficient recovery. As for the person who took a 2 hour nap in the day, the intensity of the need to sleep is lesser and the amount of recovery is reduced with the reduced amount of deep sleep.


Steps to Help Fall Asleep Faster

There are situations where the body needs sleep but, you cannot fall asleep.
The following steps can help get a better quality sleep and get into sleep stages faster.

Maintain a fixed sleep schedule

Set a consistent sleep time and wake time, make it a habit by going to bed at the same time regularly and wake up after 8hours feeling rejuvenated (Robson, 2008).
Avoid long naps during daytime.
A 15 to 20 minutes nap is enough to pay for an hour sleep credit and boots your alertness and physical stamina. A long nap during the day will make difficult to find sleep when the body needs to sleep.
It is important to sleep for a long time in the day, if you will work in the night long.

Make a perfect sleep environment

The more positive you make your sleep environment, the better sleep condition you get. Keep the room dark, exposure to light while sleeping my disrupt the internal body clock; keep the room fresh aired, quiet, good temperature not too hot and not too cold, make the bed comfortable, neat with clean beddings. For some people it is difficult to find sleep in a warm environment, it is therefore, important to sleep in the temperature that makes your sleep comfortable.
Exercise regularly
Have an everyday exercise schedule of at least 30minutes. Could be a walk, run, or any light workout that will help squash your energy of the day. As said Robson; “ a body that is healthy as a result of exercise and a good diet will not only perform better during the hours of wakefulness, it also rest better during sleep” (Robson, 2008). Exercise 3 hours earlier before bedtime, let the body get a bit tired but not too exhausted, and then have a nice and warm bath an hour prior to bedtime, it helps unwind and promote sleep.

Be mindful of the food and drink you take in

• It is advisable to eat light foods that contain Tryptophan (Melatonin) which can help get sleep quickly. For example, banana, figs, warm milk.

• There are foods that contain high levels of tyrosine; these are foods with high protein, carbohydrates or sugar. For example, peanuts, Tuna, yogurts, soy beans, turkey, etc.
Don’t take these foods one hour before bedtime Tyrosine in them can interfere with sleep. Also, it is not good to have very spicy foods like hot curries earlier to bedtime. Avoid foods and drinks with caffeine (chocolates, coffee, etc.), tea, cola, cocoa, nicotine, alcohol.

• Don’t go to bed too hungry or too full, it can keep you awake.
People have different standards of having their daily meals. Some prefer having a small breakfast and lunch then have a big dinner in the evening. As long as sleep is concerned, it’s healthier to have a big breakfast and lunch, then have small meal for dinner 3 hours prior to bedtime so it does not result in reflux, heartburn, or heartburn.

Don’t stress out

It is always uneasy to find sleep when you are stressed, the best thing to do is to note down everything that is stresses you out, it will help you release all your internal chatter that interfere with your sleep.
• Release all your worries, anxiety, fear, depression, and all other emotionally stressful matters.
• Listen to soft music
• Read a book
• Think of positive solutions
• Exercise relaxation technics
• Deep breathing , this video explains more on breathing exercises

http://www.youtube.com/watch?v=s340IhGjjc8&feature=player_embedded from www.normalbreathing.com
For more help on stress relaxation exercises read, The Stress-Free Guide to Studying at University by Rugg, Gerrard, & Hooper, (2008).

Relaxing the brain

• Try to turn off mentally; avoid excessive mental activities (Robson, 2008).
• Make an interesting story to yourself, at the end or before the end of the story you will be sleeping ready.
• Think of anything that is really boring that will make your brain work slowly.
• Count very slowly from 100 sheep to 0, the sheep or any other word you are saying in between each number will make your brain forget the following number. Don’t count so fast, otherwise it might not slow the brain movement. At the time you reach at 90 sheep you be falling asleep ready; also you can sing a song that you don’t know all the lyrics, etc.
• Move your finger and start watching its movement

• Imagine yourself being on the most beautiful beach you ever been to, or intend to go to.
• Imagine winning Lotto and spending your money on a nice holiday motel.
If these imaginations are not working for you, get off the bed leave the lights off, read a book from a different room and then return to bed when you feel drowsy.
Scent oils
Some scent oils are good for sleep for example Vanilla essential oil and scent of lavender; they help in making someone nod off faster than normally, and this helps you get into Rapid Eye Movement quickly (REM).
• Put 2 to 3 drops on of Vanilla scent oil or scent of Lavender on a tissue then put under the pillow

Change the sleeping position

Many people don’t know how they can control their positions while sleeping because they are unconscious; but it becomes easy if you can only make it a habit. Others find it hard sleeping upright on their backs; however, sleeping on straight upright on the back makes the muscles to relax then make people fall in dream stage quickly.
NB: For extended helpful information on sleep faster problems, go to www.howcast.com


Understanding the different stages of sleep and the importance of deep sleep, we can plan ahead to ensure we receive the required amount of deep sleep for recovery. On the other hand, we can also adjust our sleeping hours and patterns based on the understanding of the Homeostatic component of sleep. For example, if there is a need to operate a flight in the middle of the night, a 2 hour nap in the early evening can be taken to ensure sufficient rest to lower our need to sleep during the flight. Also, we know that within 2 hours, we are able to receive a decent amount of deep sleep.

We can also take precaution, knowing that if we sleep for short periods, we may not be lowering our heart rate enough to rest properly. Also, if we wake from a sleep when we are in the deep sleep stage (approximately 40 minutes into sleep), our level of alertness will be greatly reduced as our brain waves take time to reorientate itself. This will become more crucial when operating multiple crew details with rest periods on board a flight.

Finally, since pilots are not able to fit their schedules into the Circadian cycle or Homeostatic cycles due to the requirements in our roster, we have to understand what affects these cycles and make the necessary changes to adjust these cycles to accomodate our next flight to ensure we get a good rest and remain alert.

1. Rhythmicity of Human Vital Signs http://www.circadian.org/vital.html
2. I. Tobler and P. Achermann (2007) Sleep Homeostasis http://www.scholarpedia.org/article/Sleep_homeostasis
3. F. Halberg (2010) //Circadian Rhythms http://www.scholarpedia.org/article/Circadian_Rhythms
5. V. Baptista (2006) //Starting Physiology-Understanding Homeostasis http://advan.physiology.org/content/30/4/263.full
7. M. Smith, L. Robinson and R. Segal (2011) //How Much Sleep Do You Need http://helpguide.org/life/sleeping.htm
8. Caldwell, J. L. (2006). “Physiology of Sleep and Wakefulness, Sleep Disorders, and the Effects on Aircrew.” In Rainford, D. J., and Gradwell., D. P. //Ernsting’s Aviation Medicine. London: Hodder Education. p. 257-272.
9. Campbell, R. D., and Bagshaw, M. (2002). Human Performance and Limitations in Aviation. UK: Blackwell Science Ltd. p. 170-177.
10. De Landra, J., Boag, C., and Fletcher, A. (May 2003). "Asleep at the Control." Vector, p. 8-11.
11. Reinoso-Suarez, F., De Andres, I., Garzon, M. (2011). Functional Anatomy of the Sleep-Wakefulness Cycle: Wakefulness. Germany: Springer-Verlag Berlin Heidelberg. p. 1-4.
12. Robson, D. (2008). Human Being Pilot: Human Factors for Aviation Professionals. Australia: Aviation Theory Centre. p.141-162.
13. Sleepdex. (n.d.) All about Sleep. Retrieved April 18, 2012, from http://www.sleepdex.org
: 14 :Rugg, Gordon; Gerrard, Sue; Hooper, Susie, Apr 18, 2008, The Stress-Free Guide to Studying at University. SAGE Ltd., London , ISBN:9781849205108
14. How to Fall Asleep Fast. Retrieved Dec.,2011 www.normalbreathing.com

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