week 9: why do we sleep?

two process model of sleep

  • sleep propensity vs circadian rhythm

  • sleep homeostasis = sleep debt following wakefulness → sleep propensity (need to sleep)

  • circadian rhythm = regulated by suprachiasmatic nucleus

high prevalence of sleep issues in children and young people - see slides for stats

  • sleep problems correlated w/ mental health difficulties

dyssomnia = difficulty falling asleep/maintaining sleep

parasomnia = abnormal movements/activity/behaviours/dreams

measuring sleep:

  • subjectively = sleep diaries/questionnaires

  • objectively = polysomnography/actigraphy

correlates w/ sleep problems:

  • adversely associated w/

    • mental health - emotional/conduct problems, hyperactivity, peer relationships

    • physical health

      • less sleep causes more weight gain/dizziness/headaches/smoking/fizzy drinks/screen time

      • less sleep causes less physical activity/general health/vegetable consumption

    • psychosocial health - emotional/school/social functioning

  • community sample - poor sleep affects all demographics of children

  • more severe sleep problems = more severe mental/physical/psychosocial health difficulties

benefits of sleep for memory

  • semantic knowledge = word learning/memory of stories improves after children nap

  • episodic memory = memory for events - old vs new object identification improved after napping

  • procedural memory = faster learning how to adapt body to complete task after napping

  • working memory = holding information in brain short term

  • sleep supports memory by

    • promoting memory and neuroplasticity

    • neuroplasticity important for acquiring new info and developing skills

    • until 2 - children spend more time asleep than awake

  • children w/ insufficient sleep

    • less grey matter in brain areas responsible for

      • attention

      • memory

      • inhibition control

    • lower cognitive performance

      • vocab learning

      • crystallised intelligence

sleep disturbances correlated w/

  • emotional difficulties

    • 88% of children w/ anxiety report a sleep problem

    • greated sleep latency/night awakening

  • behavioural difficulties

    • sleep problems common w/ adhd

    • bedtime resistance/sleep initiation difficulties/night awakenings

    • indications for aggression/conduct disorder/addiction linked to sleep problems

  • sleep during infancy predicts anxiety

    • more sleep reduces risk of generalised anxiety disorder/developing social phobia

    • less sleep increases risk of emotional disorder diagnosis/separation anxiety/fear of physical injury

  • see slides for bidirectional relationship between poor sleep and emotional/behavioural difficulties

  • sleepiness facilitates development of fear cognitions/behaviours

sleep/daytime functioning in children w/ insomnia

  • daytime sleepiness predicts more social problems

  • less frustration tolerance

  • more aggressive behaviour problems

  • more concentration problems

  • more delinquent behaviour

sleep restriction vs emotional responses

  • lower ratings of positive affect

  • lower levels of arousal to positive images/movies

  • expressive arousal decreased for positive and negative images

  • increased respiratory sinus arrhythmia

research problems:

  • different measures of sleep used in different studies

  • inconsistencies in what constitutes a sleep problem

  • developmental stage of ppts

  • genetic/environmental factors likely to play a role in assocations