sleep across the lifespan

• Sleep


  Necessary for repair and restoration of the body and mind, including repairing tissues, replenishing neurotransmitters, and removing waste products
• Sleep


  Serves an adaptive function by giving us time to conserve energy and remain safe during times of potential danger, such as night-time for humans
• Sleep


  Allows for information acquired throughout the day to be processed and consolidated, aiding in memory and preparing us for the new day to come
• Characteristics of sleep that can change over the lifespan

  • Sleep onset
  • Sleep duration
  • Awakenings during sleep
  • Proportion of REM sleep
  • Proportion of NREM sleep
• Neonate (newborn)


  • Sleep duration is approximately 16 hours (not all at once)
  • In the first two weeks, neonates spend approximately 50% in NREM and REM sleep
  • From birth - 2 months old, sleep onset may occur at any time of the day or night with no regular circadian rhythm
  • Sleep duration (sleep episode) tends to be quite irregular ranging from 30 minutes to 3 or 4 hours - the baby will then have a period of wakefulness before falling back asleep
  • Babies usually only have one or two sleep cycles at a time
  • Sleep onset also occurs through REM sleep
  • The sleep paralysis associated with REM hasn't started yet so the baby may appear restless with body movements
• Infant's sleep


  • Sleep duration 13-14 hours
  • 40-30% of sleep episode is REM sleep
  • At around 2-3 months old, the babies' circadian rhythms start to exert their influence, specifically in regard to the production of melatonin
  • Environment cues such as light begin to influence the sleep cycle as well as social cues (bath/bed routine)
  • Infants begin to sleep longer at night (although the total hours of sleep reduces to about 14 hours)
  • REM-NREM cycles become more regular
  • Individual sleep episode duration extends to 5 to 8 hours by 6 month old, then the full 13-14 hours by 12 months
  • Sleep paralysis typical of REM sets in
• Children's sleep


  • Sleep duration = 13-10.5 hours
  • 25-20% of sleep episode is REM sleep
  • Total sleep time continues to decline as the child gets older, decreasing from approximately 13 hours at the age of 2 to approximately 11 hours at the age of 5
  • Proportion of REM also continues to decrease and NREM proportion increases (with greater proportion of time spent in NREM)
  • Children spend substantially more time in deep sleep (NREM 3) than adults
• Adolescent's sleep


  • Total sleep time decreases to about 10-8.5 hours
  • REM drops to approximately 20% and remains this way for the rest of the lifespan
  • NREM stage 3 sleep progressively declines, more time is spent in NREM 2 as compared to childhood
• Adult sleep


  • Total sleep duration sit at about 7-8 hours
  • Approximately 20% of sleep is comprised of REM sleep
  • Progressive decline in the amount of NREM 3 throughout adulthood (about 2% per decade)
  • By 60 years old, this decline is quite evident
• Elderly sleep


  • Total sleep duration drops to only about 6 hours
  • 20-25% REM
  • Very little (if any) NREM 3 slow wave sleep, primarily NREM 2
  • Greater difficulty with sleep onset (falling asleep)
  • Sleep becomes more fragmented, with more wakening's
  • Become sleepier in the early evening and wake up earlier in the morning (advanced sleep phase disorder)
  • As we age, we are also more likely to nap during the day
  • Sleep disorders also become more prevalent in old age