The nature of sleep and lifespan changes

The nature of sleep and lifespan changes

1. Infancy

   • Sleep 16 hours a day
     • Not continuous
     • Sleep cycles shorter than 90 minutes
   • By 6 months old a circadian rhythm is established
   • By 1 year infants sleep mainly at night, with some naps during the day
     • Periods of deep sleep lengthen and there is reduction in REM sleep
   • Evaluation
     • Daytime sleep adaptive mechanism - makes life easier for parents
     • REM sleep linked to production of neurotransmitters and consolidation of memories

2. Childhood

   • By age 5 children have EEG patterns that look like those of an adult but they sleep more (12 hours a day)
   • Still more REM activity than adults (30% of sleep time)
   • Boys sleep more than girls
   • Not uncommon for children to experience parasomnias such as sleep walking or night terrors

3. Adolescence

   • Need for sleep increases slightly from childhood: 9-10 hours a night
   • Circadian rhythms change so teenagers feel more awake later at night and have phase delay (more difficulty getting up early)
   • Evaluation
     • Change in sleeping pattern
       • Hormones primarily released at night
     • Real world application
       • Wolfson and Carskadon (2005)
         • Recommended school should begin later

4. Adulthood

   • Sleep 8 hours a night
   • 25% REM sleep
   • Parasomnias less likely but other sleep disorders such as insomnia is more likely
   • Older people have more difficulty going to sleep and wake up more frequently
   • Evaluation
     • Kripke et al. (2002)
       • Surveyed over 1 million adult men and women and found that people sleeping for only 6 or 7 hours had a reduced mortality risk, whereas those sleeping 8 had a 15% increase in risk of death, and over 30% for people who slept 10 hours. However, there may be other factors affecting this such as underlying illness
     • SWS sleep is reduced in old age explaining why older people are more easily woken
       • Van Cauter et al. (2000)
         • Less SWS means less growth hormones which explains lack of energy and lower bone density in older people