Sleep

• The purpose of sleep- Evolutionary


  1.      Evolutionary (adaptation theories): early humans are thought to have slept at night due to daytime being a safer time to eat, avoiding predators and sleeping at night allowed for energy to be conserved.
• The purpose of sleep- Restorative 


  (recuperation theories): homeostasis is disrupted when humans are awake and sleep acts to restore the energy lost during the day.
• The sleep-wake cycle


  The reoccurring pattern of wakefulness and sleep that individuals experience daily.

  • It is usually measured by recording the times of regular events (sleeping, eating etc)
  • It is regulated by the circadian rhythm, body temperature, metabolic rate and specific hormones such as melatonin.
• Circadian rhythm


  bodily cycle of approximately 24 hours that controls the nocturnal release of some hormones (melatonin).
• Melatonin


  the hormone that regulates the sleep-wake cycle.
• Benefits of Sleep


  General physical health, energy restoration, Recovery from injuries or illness, growth and psychological well-being, mood regulation, improved concentration and memory, better work performance and social interactions.
• Sleep Cycles


  Each cycle lasts around 90 minutes. Cycles consist of different stages (deep and light sleep). Sleep stages change as the night progresses.
• Types of Sleep


  Two main types: REM (Rapid Eye Movement) and NREM (Non-Rapid Eye Movement). Healthy sleep includes both REM and NREM sleep.
• NREM Sleep


  This is the first stage experienced when falling asleep. Each stage involves progressively deeper sleep. NREM sleep is important for body restoration and repair: Restores hormone levels, Repairs muscles and tissues, Detoxifies muscles. Stage 3 is vital for feeling refreshed and non-fatigued in the morning.
• REM Stages:

  STAGE 1: light sleep, transition phase between wakefulness and sleeping

  STAGE 2: Light NREM sleep marked by sleep spindles and K-complexes

  STAGE 3: slow-wave sleep (SWS) deepest stage of NREM sleep
• Stage 1: NREM Sleep: light sleep, transition phase between wakefulness and sleeping


  Stage 1 NREM lasts approximately 1 – 10 mins.

  Entering Stage 1 NREM Sleep:

  Occurs as you start to relax. The nervous system slows down: heart rate decreases, breathing becomes irregular, muscles relax.

  Hypnogogic State: Transition between wakefulness and Stage 1 NREM sleep and is characterized by slow, rolling eye movements that stop once an individual falls asleep.
• Stage 2: NREM Sleep: Light NREM sleep marked by sleep spindles and K-complexes


  Progression of Sleep: Sleep deepens, body temperature drops. Heart rate and respiratory rate continue to slow. Eye movement stops and muscles continue to relax and there are occasional muscle twitches.

  Duration: The first time this stage occur in the night it lasts approximately 10 to 30 minutes, then increases in length with each repetition of the stage.
• Stage 3: NREM Sleep: slow-wave sleep (SWS) deepest stage of NREM sleep


  Heaty rate continues to decrease, minimal eye movement, muscles are at their most relaxed. 20-40 minutes is the time spent in this stage for the first few sleep cycles and then they reduce in length. Physiological responses steady, entering deep sleep, making the sleeper more difficult to wake.
• Slow-Wave Sleep (SWS): Stage 3 NREM

  Marked by almost pure delta brainwaves. Reached after about an hour of entering the sleep cycle.
• Waking from Stage 3: NREM 


  If woken, the sleeper may be confused and disoriented. May take a few minutes to regain full awareness.
• REM sleep


  • rapid eye movements, indicating high brain activity.
  • Strongly associated with dreaming
  • Heart beats faster and generally increased to match the rate when awake but varies depending on dream content, breathing is rapid/irregular, and eyes move under eyelids.
  • Skeletal muscles are in a state of atonia (paralysis) except for muscles involving breathing and the eye.
  •   First REM period occurs about 90 minutes after falling asleep. Lasts for 10-60 minutes, and stages increase in duration over the night ranging from a few minutes to one hour
• The Sleep-Wake Cycle


  Sequence of a Sleep Cycle:

  Stage 1 NREM: Entered only once during the first cycle.

  • Progression: After Stage 1, the sleeper moves through Stage 2 and Stage 3 NREM sleep, entering deeper sleep.
  • Reversal: After reaching Stage 3, the sleeper moves back to Stage 2 NREM.
  • REM Transition: Instead of re-entering Stage 1, the sleeper transitions from Stage 2 NREM into the first REM sleep period.

  •       The cycle then repeats with:

  •       Stage 2 NREM

  •       Stage 3 NREM

  •       Stage 2 NREM

  •       REM Sleep
• The Sleep-Wake Cycle- information

  •       Sleep consists of cycles that are approximately 90 minutes in length.

  •       Each cycle includes various stages of sleep.

  • NREM sleep duration shortens as the night progresses.

  • REM sleep lengthens potentially lasting up to an hour in later cycles.

  • EEG is used to measure brain neuron activity which can help identify the types and stages of sleep, used in conjunction with physiological changes.
• What is sleep deprivation?


  Sleep deprivation is the condition of not getting sufficient sleep. When an individual doesn’t get enough sleep (quantity) or adequate quality sleep, they experience sleep deprivation. Functioning during the awake state may become more difficult.
• Partial Sleep Deprivation


  results when people get some sleep, but not enough (in quantity or quality) to support their normal waking alertness, performance or health.
• Chronic Sleep Deprivation:


  occurs when individuals are sleep deprived over a prolonged period (days, months or years).
• Causes of sleep deprivation-Drugs

  •       Many drugs (both illicit and legal), specifically those that are stimulants can cause sleep deprivation. Depressants like alcohol can cause people to wake up when the drug wears off. Stimulants like caffeine increases the activity of the central nervous system, affecting an individuals ability to go to sleep and stay asleep for a sufficient amount of time.

  •       They can also affect sleep stage progression by reducing the amount of NREM or affecting REM sleep.
• Causes of sleep deprivation: Shift work


  •       Shift work involves altering the sleep-wake cycle and consequently reduces the quality and quantity of sleep.

  •       Sleeping during the day is hard too due to light and sound exposure, impacting and individuals hormones from properly regulating their sleep-wake cycle.
• Causes of sleep deprivation: Sleep environment:


  Brightly lit environments may reduce the amount of melatonin secreted, thus disrupting sleep-wake cycles. Environmental noise can wake individuals and decrease their intensity of sleep.
• Causes of sleep deprivation: Stressors


  Family issues (disputes or difficulties), problems at work or school, illness, death etc can make it difficult to fall and stay asleep (anxiety related). Stressors also impact sleep routines and result in less sleep overall
• Effects of Partial Sleep Deprivation


  Occurs because of a short-term lack of sleep over a 24 hour period or up to a few consecutive nights with less than five hours of sleep within a single 24 hour period. Common causes include illness, finishing an assignment late, jet lag and stress. The immediate effects of this type of sleep deprivation can be typically reversed with adequate sleep.
• Effects of Partial Sleep Deprivation: Mood


  •       Sleep helps regulate emotions and deprivation is detrimental to mood and emotional stability, amplifying emotional responses. It also affects the ability to process emotional information, put it into context and produce controlled and appropriate responses.

  •       More frequent disrupted sleep increases the tendency for people to experience more negative emotions and even develop mood disorders (anxiety and depression).
• Effects of Partial Sleep Deprivation: Attention

  •       Sleep is essential for cognitive (thinking) performance ranging from simple attention and alertness to higher-order executive function.

  •       Spatial orientation deteriorates, and thinking may become irrational and illogical.

  •       Attention control and sustained concentration become difficult, reducing the ability to perform tasks to a set standard (Durmer & Dinges, 2005).
• Effects of Partial Sleep Deprivation: Reaction time


  •       REM sleep is linked to learning tasks, and disruptions in REM sleep impair subsequent task performance

  •       Sleep deprivation reduces the ability to complete simple, monotonous, or repetitive tasks, especially those requiring reaction speed or vigilance.

  •       Reaction time to sudden changes in circumstances slows, leading to performance variations and increased errors (Doran et al., 2001).

  •       These effects make activities like driving, playing contact sports, or using power tools highly dangerous when sleep deprived.
• Effects of Partial Sleep Deprivation: Vision


  Vision can become blurry, eye spasms may occur, and eyes become increasingly sensitive to light
• Effects of Chronic Sleep Deprivation

  When sleep is inadequate for more than a few weeks at a time, chronic sleep deprivation can occur. Sleep disorders like insomnia, lifestyle choices and other factors like work can cause chronic sleep deprivation. Chronic sleep deprivation leads to more adverse side effects and health issues than partial sleep deprivation and it is more difficult to reverse.
• Effects of Chronic Sleep Deprivation: Diseases

  Heart disease – increased blood pressure and cholesterol levels are common side effects. These can lead to heart disease.

  Obesity – chronic sleep deprivation often leads to people consuming energy rich foods and the amount of food they eat.

  Insomnia – A sleep disorder characterised by difficulties falling asleep or difficulties staying asleep (low sleep latency). It is also common to wake up feeling unrefreshed.

  Anxiety – emotional regulation is negatively affected by chronic sleep deprivation and this can exacerbate symptoms of anxiety.
• Sleep Hygiene


  •       ‘Sleep hygiene’ refers to habits, behaviors and environmental factors that can be adjusted to help individuals have a healthy sleep.

  •       Sleep hygiene can be improved by the management of electronic devices, consistent sleep patterns, and a creation of a healthy sleep environment
• Management of Electronic Devices


  •       Sunlight is the main source of ‘blue light’ so exposure to sunlight during the day will provide the signal to make us alert and awake.

  •       As the sun goes down at the end of the day, it cues the pineal gland to release melatonin, and we will begin to feel drowsy.

  •       By limiting your exposure to ‘blue light’ in the 1 to 2 hours before bed, sleep onset will be easier to achieve. This increased brain stimulation leads to heightened cognitive alertness and so sleep quality and duration is likely to be affected.
• Consistent Sleep Patterns


  Consistent sleep patterns can increase the amount and duration of sleep and aids in regulating the circadian rhythm (internal body clock), and prevent sleep deprivation. This can be done by setting a bedtime that allows for the recommended amount of sleep according to the age of the individual.
• Creation of a healthy sleep environment


  Circadian rhythms can change due to an uncomfortable sleeping space. The bedroom and bed should be free of distractions and should be used only for sleep or intimacy – creating the cognitive link between the bed and sleep.
• Study: Effect of restricting bedtime mobile phone use on sleep, arousal, mood and working memory (HE ET AL., 2020): Aim


  To determine how limiting the use of mobile phones before bedtime affects mood, working memory, pre-sleep arousal, sleep quality, and sleep habits.
• Study participants:

  Thirty-eight university students who had the habit of using their mobile phone before bed as well as experiencing poor sleep quality.
• Study Materials

  Positive and Negative Affect Schedule (PANAS), n-back task, Pre-sleep Arousal Scale (PSAS), Pittsburgh Sleep Quality Index (PSQI) and an online sleep diary.
• PANAS:


  self-report measure consisting of 20 statements each requiring the completion of 5-point Likert scale positive and negative emotions over the past week are assessed.