AQA PSYA3 - Biological Rhythms - Lifespan Changes in Sleep


Prenatal sleep

  • Okai (1992) studied REM and NREM of unborn babies of 30 pregnant women.
    • By 32 weeks REM could be identified. 
    • This correlates with development of neural structures in the brain which are known to be responsible for sleep stages.


  • Spend an average of 16 hours sleeping per day.
  • Shorter cycle than adults.
  • Have 2 sleep stages; quiet sleep and active sleep. 
    • These are immature versions of SWS and REM.
  • In first months sleep is equally divided between the two.


  • By 6 months a circadian rhythm is established.
  • By 1 year infants sleep mainly at night.
  • SWS lengthens and REM reduces.


  • 5 years: have adult EEG pattern, but sleep 12 hours per day. Sleep is 30% REM.
  • Boys sleep more than girls.
  • Need for sleep gradually decreases.


  • Sleep increases to 10 hours per day.
  • Circadian rhythm changes; feel more awake at night, find it difficult to wake up early (phase delay).


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