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Sleep - Y2 - Coggle Diagram
Sleep - Y2
Improving sleep
Sleep hygiene - trait sleep quality can be improved by practice and learned behaviours
- Sleep hygiene refers to the practices and behaviours a person habitually exhibits with the purpose of instigating good sleep - a persona can have good or bad sleep hygiene, depending on their behaviours which directly influences their sleep
Generally, sleep hygiene measures several test categories -
- Stimulants - does the individual take substances or perform behaviours before bed
- Attitude - does the individual go to bed upset, stressed, angry, anxious or relaxed, satisfied, happy etc - anticipation of potential events is also a cognitive stimulant
- Environment - is the typical sleeping environment disruptive or calm
- Habits and routine - the classic definition of sleep hygiene; does the individual follow a strict routine prior to going to sleep, routine is a consistent predictor of good sleep quality (onset latency) - LeBourgeois et al, 2005
Lifestyle -
- State sleep quality can be improved by changes to daily actions and lifestyle
-> Music - listening to 45 minutes if classical music at bedtime improves subjective sleep quality, compared to an audiobook and control condition (Harmat et al, 2008)
-> Exercise - over 12 weeks, high and low intensity physical activity training improved subjective and objective sleep quality compared to no additional exercise - effect was stronger in men than women (Jurado-Fasoli et al, 2019)
-> Yoga - weekly sessions and additional self practice improves subjective and objective sleep quality (Guerra et al, 2020) -
--> Lots of research shows the detrimental effect of rumination, stress, and anxiety on sleep quality with self-compassion as a buffer - self compassion is the mechanism through which yoga improves speech
-> Electronic devices - 2 week intervention on students with burnout and poor sleep quality
--> Participants provided a sunrise alarm clock where all electronic devices in bedroom were turned off
--> Self-reported sleep quality and burnout improved after the two weeks (Brubaker et al, 2020)
- Sleep hygiene - consistent routines improve body’s recognition of sleep times, and thus quicker release of these hormones
- Use for your bed / bedroom for sleep only - reset button for neural sleep activity when you move rooms
- Exposure to natural light - spending a lot of the day under artificial lighting impacts sleep
- Do not nap during the day - napping uses up accumulated sleep hormones (CLOCK) and confuses your brain out of natural biphasic circadian rhythms
- Run your hands under cold water - core body temp decreases in sleep, and cooling down before sleep helps with this process; also put on the back of the neck as this is the quickest route to the CNS
What is sleep?
Sleep is a behavioural and cognitive state of perceptual disengement from the environment - 'body rests but brain sleeps' (Hiroshkowitz, 2004)
- Disengaged from the environment, but more in tune with the self / internal bodies
Defining components -
- Non-permanent state of subconsciousness
- Natural rhythms - sleep states and cycles, circadian rhythms and sleep spindles
- Common (not necessary) behaviorual components / indicators
-> Closed eyes, slower breathing, limited muscle movement
Sleep stages - Carskadon and Dement, 2005:
- NREM - non-rapid eye movement
- Low muscle tonus (flexibility and activity)
- EEG shows slow frequency waves indicative of reduced neural activity
- Dreaming is possible but less vivid
- 3 substages characterised by neural waves -
-> Stage 1 - theta waves - transitional stage between sleep and wakefulness
-> Stage 2 - sleep spindles - sleep stabilises into average depth, roughly 50% of our sleep duration is N2
-> Stage 3 - delta waves (SWS) - deepest sleep, critical period for many restorative functions
- REM - Rapid eye movement -
- Atonia (temporary sleep paraylsis)
- EEG shows high frequency waves indicative of waking neural activity (paradoxical sleep)
- Dreams occur here and are vivid and complex
Sleep cycles - last around 90 minutes - this can change with age:
- Level of sleep is characterised by brain waves
-> Alpha and gamma waves - waking (gamma for cognitive effort)
-> Beta - REM
-> Theta - NREM 1
-> Sleep spindles + k complexes - NREM 2
-> Delta waves - NREM 3
- Throughout the 90 minutes, we go back up from Stage 3 to Stage 2, then REM starts after this point and increases in length throughout the night (Mander, Winer & Walker, 2017)
Circadian rhythms - natural 24 hour rhythms of biological processes that regulate the sleep-wake cycle:
- This is governed by a specific brain region - suprachiasmatic nucleus (SCN)
- Also includes digestion, hormone release, and body temperature
- Governed by external cues (zeitgebers) such as light, social interactions, temperature
-> These help to regulate the cycle, but can be manipulated (e.g. habits or desynchronisation from zeitgebers)
-> Siffre (1962) - cave study
Chronotypes - A phase marker of individual differences in circadian rhythmicity - adaptive for survival and protection in groups
- Some people are biologically designed to sleep and wake with the rising / setting sun - other people are more alert later in the day and others earlier
- Michael Brues (not reliable) - 4 chronotypes; lion, wolf, bear, dolphins
-> Lions are early risers, dolphins are insomniacs, bears follow normal patterns and wolves are night owls
- Research -
-> Chronotypes remain a theoretical construct with no specific gene identified
-> However, evening types are well associated with mood disorders (Taylor and Hasler, 2018) including depression (Hidalgo et al, 2009), SAD (Johansson et al, 2003) and bipolar disorder (Giglio et al, 2010)
-> Evening types obtain lower grades but the effect of chronotype on academic performance is moderated by the time of day of the testing (Zerbini and Merrow, 2017)
Extra reading on sleep
Functions and mechanisms of sleep (Zielinksi, McKenna and McCarley, 2016):
- Essential for vital functions such as development, energy conservation, brain waste clearance, modulation of immune responses, cognition, performance, vigilance, disease and psychological state
- Regulated globally, regionally and locally by molecular and cellular mechanisms
- Redundancy in the molecules, cells and neural circuitry regulating sleep suggests sleep plays a crucial and protective, physiological role
Governing the world of wakefulness - exploration of alertness, performance and brain activity (Ahleim):
- Tested ‘stay-awake men’ - researchers tested methods of measuring alertness, validated and modified theories about sleep, and how perception of being awake has changed over time
Memory process and the function of sleep (Zhang, 2004):
- Function of sleep is to encode and transfer the data from the temporary working memory to long term memory
How does sleep affect the perception of facial emotion? - Beattie, 2018:
- Moderated by the task used
- However, evidence suggests that sleep does affect emotion perception
-> Sleep affects social interaction in terms of decoding and creating signals
-> Emotion generation and regulation is not discrete, and sleep disruption affects aspects of facial appearance which may be differentially processed in insomnia
-> Sleep impacts visual perception and therefore facial recognition and matching of unfamiliar faces
The role of sleep in cognition and emotion (Walker, 2009):
- Wake and sleep are involved in coordinating the encoding, consolidating, and integration of memories
- Overnight modulation through sleep of affective networks and integration with previously encountered emotional experiences
Summary
- Sleep is one of the most important functions of the human body, and is integral to behaviour, attitude and cognition
- Sleep deprivation studies are an excellent method to demonstrated the effects of sleep loss
- Sleep is more than temporary lack of consciousness, it is an opportunity to disengage from external output and manage internal processes
- Why we sleep is a very heavily explored subject, but with no definitive answer
-> All leading and reliable theories of sleep generally fall under evolutionary theories
- Due to the lack of consciousness and issues of invasiveness and reliability, studying the effect of sleep is difficult - recent research has highlighted the necessity for utilising a combination of methods, and separating components
- Sleep is directly related to many symptoms of health, so plenty of research explores the best ways to improve sleep, while some methods are generally effective, we must remain critically evaluative
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Measuring sleep
Sleep is conceptually vague, with inconsistent definitions and measurements, and this makes studying sleep very difficult and applying general and consistent findings in a wider setting
- There are several methods that are typically used in sleep research
Polysomnography - typically referred to as the gold standard for sleep research:
- Found in sleep labs where the participant stays the night
- A series of devices which are connected to a particpant to record brain waves, blood oxygen levels, heart rate, breathing and limb movement
- Generally considered very accurate and reliable when studying various components of sleep
- EEG, EOG/ECG, oronasal airflow, chin EMG, position sensor, pulse oximetry, thoracic and abdominal movements, control uni
- However, they are expensive and resources are not always accessible, and as it is an artificial environment
Which method should we use?
- Accuracy and reliability - polysomnography
- Control - polysomnography
- Invasiveness - actigraphy or self-report
- Ethical considerations - actigraphy or self report
- Cost and access - self-report
- Purpose - self-report best for subjective sleep satisfaction
-> Actigraphy best for natural sleep physiology
-> Polysomnography best for in-depth physiology
Actigraphy - a wearable device that can be worn anywhere, enabling sleep to be studied at home:
- The wristwatch-like device records muscle movement, as a proxy for various components of sleep - atonia in REM sleep
- Very practical measure of natural sleep
- However, muscle movement does not always equate to sleep - the measure can therefore be affected by napping and peaceful wakefulness
- It can distinguish NREM and REM but not a specific stage - its starts recording when you do not move for a while
- Blood et al (1997) - actigraphy is a superficial measure, does not account for peaceful wakefulness
Lee and Lawson, 2021 - recorded participants sleep quality via both self-reported surveys and actigraphy to examine the effects of sleep health on perceived stress
- Greater perceived stress positively predicted greater sleep health problems
- However, they measured sleep health via a composite score generated from combined actigraphy and self-reported sleep data
- When separated, the study found that actigraphy-measured sleep duration was not associated with perceived stress, however self-reported sleep satisfaction was
- This study well highlights the importance and effect of sleep measurement method
-> Does sleep health predict stress - perhaps subjective sleep satisfaction does, but objective sleep duration does not
Experimental manipulation - sleep deprivation; preventing total sleep for a full night or more:
- Often associated with damaging cognitive functions, although recent research suggests therapuetic sleep deprivation may be an effective treatment for some psychological disorders (depression, insomnia)
Partial sleep deprivation - sleep deprivation is not only the total absence of sleep, but rather the disruption of typical sleep
- You can be sleep deprived if you slept only 4 hours, rather than your normal 8 hours
- Therapies utilising sleep deprivation argue over which stages of sleep must be deprived in order to treat symptoms of depression and insomnia - insomnia is treated by being awake for one night and sleeping the next
- For depression, you deprive them of REM sleep, you can subdue symptoms - limited evidence and relapse is high
Self report - most common method, consistent correlation and reliable measure between sleep and self-report:
- However, retrospective reporting can be affected by mood and time of reporting - lack of validity
- Sleep diaries - state measures
-> Bedtime and waketime self-report surveys that are completed everyday over a longitudinal study
-> How well did you sleep last night? How many times did you wake up?
- Sleep survey - trait measure
-> PSQI (Buysse et al, 1989)
-> How well did you sleep over the last 30 days? On average, how often did you wake up during the night?
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