What is Insomnia, what factors cause it and what can we do?
Have you woken up during the night and not been able to get back to sleep?
Do you have problems getting to sleep before the start of early flights?
I can help to explain what may be happening and what can help!
I have worked as an Airline Pilot in the commercial airline industry in excess of twenty years and have seen first hand the effects of sleep deprivation on the health, safety and wellbeing of colleagues and service users.
My training in the Advanced Practice of Cognitive Behaviour Therapy for Insomnia (CBT-I) through the Sleep Consultancy in Edinburgh provides a pathway resolving chronic insomnia in Pilots, Air Traffic Controllers and Cabin Crew.
Sleep is a complex system of physiological (the body) and psychological (the mind), both of which go to rest for a period of time.
Sleep regulation has two components.
The first is the build-up of homeostatic sleep drive [1] which reminds our bodies to sleep after a certain period of wakefulness and regulates our sleep intensity. The longer we are awake the stronger this drive becomes and the longer and more deeply we sleep after a period of wakefulness.
The second is the regulation of our circadian rhythms [2] that control a wide variety of functions such as wakefulness, body temperature, metabolism, and the release of hormones such as melatonin. Melatonin [3] is a hormone that is developed naturally in our bodies and acts as a trigger for sleepiness. The levels increase during the night and returns to lower levels during the day. Whereas cortisol [4] secretions are lower at the initial part of sleep and increase during the end of our sleep period helping us to wake up.
Our circadian rhythms synchronize with various environmental cues which indicate the time of day. These are called zeitgebers [5] (biological clock/time givers of an organism). The main zeitgeber is daylight but other factors such as food and temperature help to prevent circadian drift [5-6], and our internal biological and psychological rhythms synchronised for optimum function.
These two components, homeostatic sleep drive and our circadian rhythm, interact to determine the time when we go to sleep and the time when we wake up. For sleep to occur our homeostatic sleep drive needs to be a stronger factor than alerting factors such as daylight, stress, anxiety, and stimulants which lead to increased alertness.
When alertness-promoting factors are more dominant, then sleep disturbances can start and maladaptive thinking, unhelpful behaviours and reactions to these disturbances can maintain them.
The American Academy of Sleep Medicine [7] (AASM) defines insomnia as a sleep disorder in which you have trouble falling and/or staying asleep. The condition can be short term (acute) or can last a long time (chronic). It may also come and go. Acute insomnia lasts from 1 night to a few weeks. Insomnia is classified as chronic when it occurs at least 3 nights a week for 3 months or more. People report of an unsatisfactory quality or quantity of sleep-in terms of difficulty in falling asleep and staying asleep, or early final awakening (also known as initial, middle, and late insomnia).
The feeling of insomnia is often symptomized by the feeling of being ‘tired and wired’, a constant feeling of tiredness, psychological fatigue, and physical exhaustion [8]. Have you found yourself lying in bed, tired but completely unable to sleep?
Some of the common causes of insomnia are stress and anxiety [9] which activate the body’s fight or flight system. Have you woken up between 2-3 am, and been unable to get back to sleep? Cortisol, the stress hormone, naturally increases around this time, helping in managing our 4 stages of sleep [10-11], Non-REM (NREM) stages 1-2-3 and Rapid Eye Movement (REM) sleep stage 4.
If we take unresolved stress or anxiety to bed with us, then more cortisol is added waking us up and keeping us awake! Outside of our awareness, the bed-bedroom-bedtime routine can trigger Classic or Pavlovian conditioning [12] which becomes a cue for emotional arousal, interfering with sleep.
Have you experienced falling asleep downstairs, but to only feel wide awake on entering the bedroom?
Irregular sleep patterns, as experienced by Pilots, Air Traffic Controllers and Cabin Crew, can affect our circadian rhythms leading to continued sleep disturbances.
There is a bidirectional relationship between mental health disorders such as depression and anxiety and our quality of sleep [13-14]. Insomnia can be a contributing factor to the onset of mental health problems. So, improving sleep can be of direct benefit to prevent or aid in the treatment of mental health conditions. The stages of sleep are [15] N1, our entry to sleep where we are easily woken by noises around us. N2, a deeper stage of sleep helping with learning and memory, although loud noises can still wake us. N3, deep sleep or slow-wave sleep (SWS, characterized by high-amplitude, low-frequency brain waves) where the body repairs and regrows tissues, builds muscle tone and strengthens our immune system. It is difficult to wake us up in this deep stage of sleep. REM, our emotional regulation stage of sleep where vivid dreaming occurs and our muscle tone is reduced in many of the body’s muscles (muscle paralysis), so we don’t act out our dreams.
Looking at the Hypnogram below, showing the sleep stages and sequence, we can see that REM sleep [16] increases through the night. If we experience prolonged awakenings between 2am to 5am, we lose a significant amount of our emotional regulating sleep affecting our mood, learning and memory formation too.
Some shift workers report experiencing sleep paralysis [17] as they enter sleep or on awakening, being classed as a ‘disorder’ as it occurs outside of REM sleep. It can last several seconds or minutes and is linked to high stress levels, excessive alcohol consumption, sleep deprivation and narcolepsy.
Sleep Loss leading to Insomnia
How well do we sleep before the first early flight or after the first late flight when we are used to going to sleep or waking up with our family and social life schedule. Sleep debt [18] refers to the accumulation of sleep loss over a given time period. The American Academy of Sleep Medicine (AASM) recommends adults require a minimum of 7 hours of sleep [19]. We restore the sleep debt by extending our sleep. When we experience circadian misalignment
[20] following shift work, this can be difficult to achieve because we try to re-align ourselves back into a regular routine with our family and social lives, but our bodies are in a different time zone. We try to stay awake when we have been going to sleep or try to sleep when we have been awake. After a few days our sleep/wake cycles become more aligned, but very soon we are back on an out-of-sync work cycle.
Sleep debt and sleep difficulty accumulates further, and maladaptive coping strategies can creep in such as taking stimulants to overcome tiredness like caffeine [21] which disrupts deep slow wave sleep (SWS), our physiological restorative sleep, thus leading to a greater feeling of un-refreshed sleep which leads to further use of stimulants. We are also more prone to illness from a degraded immune system [22] caused by disrupted sleep. Alcohol [23] is often used to try and sedate us but this disrupts/fragments REM sleep leading to more awakenings during the night which can cause a lack of emotional regulation. Anxiety builds up because of our degraded performance from sleep difficulties resulting in more disturbed sleep which increases the risk of chronic insomnia.
“Why can’t I sleep before an early duty?”
Circadian rhythms are physical, mental, and behavioural changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark. Shift work schedules go against most people’s internal body clocks or circadian rhythms. Sleep is paradoxical to the rule “the harder you try the easier it becomes”. If we go to bed at an earlier time than normal to gain more sleep before our alarm goes off in the early hours we can be fighting against our natural alerting signal for ‘awake’.
So, what can we do?
The longer we are awake throughout the day the more ‘sleep pressure’ we experience characterised by a buildup of adenosine [24], a neurotransmitter found in the human body that promotes sleep drive. These adenosine molecules break down (adenosine is flushed out of our brains by the interstitial fluid via the brain stem) as we sleep enabling the cycle to start again. Getting an early start to the day will help increase our adenosine levels and
therefore the more active we are the more adenosine is released increasing our sleep pressure, drive for sleep. Caffeine is an adenosine antagonist [25], which blocks our
brains adenosine receptors. It is therefore better to limit caffeine to the morning, especially as caffeine has a long half-life of up to eight hours. “Would you drink a cup of coffee before going to bed?”
During the day light signals slows down or stops the production of melatonin in the pineal gland, but as the daylight fades, the pineal gland starts to produce melatonin. The longer we are in darkness, or low light, the more melatonin builds and the drowsier we become. An evening routine of low light (limit screen time) low stimulation and going to bed at a low propensity for ‘awake’ will help us sleep better.
What can help with chronic insomnia?
For any insomnia treatment to be effective in the long-term, it needs to address the root causes behind sleeplessness. Traditionally, CBT-I [26] is a multicomponent treatment that combines several approaches, including sleep education, cognitive restructuring, stimulus control, and matching our time in bed to the amount of sleep our bodies are actually producing. These components support and promote the body’s natural sleep mechanisms.
Pharmaceutical interventions only mask a sleep problem, they do not offer a cure!
Do you know your chronotype?
If you search ‘MEQ Sleep Questionnaire’ [27] on the internet you
can find your chrono type.
Generally, these are:
The ‘morning type’, or early bird or Lark.
Evening/late chronotype or Owl.
Intermediate chronotype referred to as a hummingbird.
Then try to work a shift pattern that matches your chronotype. Younger adults generally have a later chronotype whereas older adults move towards an earlier chronotype.
Napping
During the day napping [28-29] can help with reducing the effects of tiredness. Methods include controlled rest during a duty. A NASA study [30] in the 1990’s found that naps
helped pilots maintain their baseline reaction speed over the course of the flight. It is better to limit this to 20-30 minutes though, because if we take longer periods than this we can enter the deeper stages of sleep, N2-N3 (NREM) where our brain waves slowdown (SWS). If we awake from the deeper stages of sleep we can experience grogginess, impaired cognitive ability, impaired visual attention, and impaired spatial memory along with sleep
inertia [31], the desire to go back to sleep, creating a risk to flight safety. Napping for extended periods, such as 1-2 hours, will also reduce our sleep pressure making it harder to fall asleep when required at nighttime.
For further information and help with sleep disorders of Insomnia, Shift Work Sleep Disorder (SWSD), Sleep Apnoea, Depression and Anxiety please visit www.sleep-focus.com
For help and advice for sleep disturbances during the Menopause and for Childrens Sleep problems, please visit www.Sleepsussed.com
This article by Mark Dobson was published in the SkyPointer Newsletter, March 2024.
References:
[1] Homeostatic Sleep Drive, Centre for Disease Control and Prevention, (2020). https://www.cdc.gov/niosh/work-hour-training-for-nurses/longhours/mod2/11.html#:~:text=Pressure%20for%20sleep%20(homeostatic%20sleep,night%20of%20good%2Dquality%20sleep.
[2] Circadian Rhythm, National Library of Medicine, (2020), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7098792/
[3] Melatonin, National Library of Medicine, (2015), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4334454/#:~:text=The%20neurohormone%20melatonin%20is%20not,inhibits%20this%20mechanism%20%5B12%5D
[4] Cortisol, Sleep.com, (2023), https://www.sleep.com/sleep-health/why-do-i-wake-up-at-3am#:~:text=Cortisol%20may%20be%20best%20known,stressed%20or%20anxious%2C%20and%20your
[5] Zeitgebers, National Library of Medicine, (2012), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3553574/#:~:text=Light%20is%20the%20strongest%20synchronizing,is%20important%20for%20optimum%20function
[6] Environmental Therapeutics, How do we stop our circadian rhythms from drifting, (2024), https://
[7] Insomnia, AASM, (2023), https://sleepeducation.org/sleep-disorders/insomnia/#:~:text=It%20occurs%20when%20you%20have,staying%20asleep%20throughout%20the%20night
[8] Burn-out, Inspired Health, (2024), https://inspiredhealth.co.uk/blogs/wellness/feeling-tired-and-wired#:~:text=Often%20symptomised%20by%20a%20feeling,but%20a%20few%20common%20symptoms
[9] Insomnia, Anxiety and Depression, National Library of Medicine (2013), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669059/#:~:text=Syntheses%20of%20longitudinal%20studies%20suggested,%2C%20but%20not%20vice%2Dversa
[10] Stages of Sleep, Cleveland Clinic (2023) https://my.clevelandclinic.org/health/body/12148-sleep-basics
[11] Sleep Stages, Polar.com, (2022), https://www.polar.com/blog/sleep-stages/#:~:text=N2%3A%20a%20deeper%20stage%20of,sleep%20or%20slow%2Dwave%20sleep
[12] Classic Conditioning, Carney (2009)
[13] National Library of Medicine, Bidirectional relationship between sleep and depression,
[14] Sleep deprivation https://aasm.org/resources/factsheets/sleepdeprivation.pdf (2008)
[15] UNDERSTANDING YOUR SLEEP STAGES | DEEP SLEEP VS. LIGHT SLEEP, (2022),
[16] REM Sleep, Sleep Station, (2022), https://www.sleepstation.org.uk/articles/sleep-science/remsleep/
[17] Sleep Paralysis, Stanford Medicine, (2024), https://stanfordhealthcare.org/medical-conditions/sleep/nighttime-sleep-behaviors/sleep-paralysis.html
[18] Sleep debt https://www.sleepfoundation.org/how-sleep-works/sleep-debt-and-catch-up-sleep (Jan 2024)
[19] AASM, Adult Sleep https://www.ncbi.nlm.nih.gov/books/NBK585109/ (July 2023)
[20] National Library of Medicine, Disturbance of the Circadian System in Shift Work and Its
Health Impact, (2022), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8832572/#:~:text=and%20metabolomic%20rhythms.-,Circadian%20Misalignment,peripheral%20clocks%20are%20usually%20entrained
[21]Caffeine, Journal of Clinical Sleep Medicine, (2013), https://jcsm.aasm.org/doi/10.5664/jcsm.3170#:~:text=The%20results%20of%20this%20study,detrimental%20effects%20on%20daytime%20function
[22], National Library of Medicine, Role of sleep deprivation in immune-related disease risk and outcomes, (2021), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8602722/
[23] Sleep Foundation, Alcohol and Sleep, (2021), https://www.sleepfoundation.org/nutrition/alcohol-and-sleep#:~:text=Alcohol%20is%20a%20nervous%20system,how%20quickly%20it%20is%20consumed
[24] National Library of Medicine, Adenosine and Sleep, (2009), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769007/
[25], Journal of Sleep Research, Adenosine, caffeine, and sleep–wake regulation: state of the science and perspectives, (2022), https://onlinelibrary.wiley.com/doi/full/10.1111/jsr.13597
[26] CBT-I, National Library of Medicine, (2019), https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6796223/
[27] Morning and Evening Questionnaire, https://qxmd.com/calculate/calculator_829/morningnesseveningness-questionnaire-meq
[28] Napping, The National Sleep Foundation (May 2021)
[29] Napping, National Library of Medicine, (2016) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763354/
[30] Pilot napping, Priceonomics, (2014) The NASA Studies on Napping - Priceonomics.
[31] Sleep Inertia, The Sleep Foundation (2023), https://www.sleepfoundation.org/how-sleep-works/sleep-inertia