The Nature of Sleep and Life Span Changes

As we grow we experience major changes in our length and kind of sleep

Babies sleep a lot more than children or adults and have different patterns and stages of sleep. 

• About 16 hours and not continuos.
• As sleep cycle shorter wake up every hour or so.
• Sleep stages called quiet sleep and active sleep (immature versions of SWS and REM sleep).
• At birth, more active sleep than adult REM, half is active sleep.
• Infants enter sleep through initial period of light sleep (20 mins gradually enter deep sleep), not like adults, can go directly into state of deep sleep.
• By 6 months circadian rhythm established. 
• By 1 year usually sleeping mainly at night with 1 or 2 naps.
• Periods of deep sleep lengthen and reduction in active/REM sleep. 
• Cannot assume babies’ REM accompanied by dream, not reliable reporter in infancy.

• Newborn babies: 

Evolutionary approach — Babies’ sleep is adaptive mechanism to make parents’ life easier. Daytime sleeping, parents can get on with chores, enhancing survival. Night waking adaptive too. Babies have small stomachs and need to be fed regularly. Baby who sleeps soundly through night might not be woken by feeling cold or hungry.

Explaining why infants are different — Infants’ greater amount of active/REM sleep = relative immaturity of infant brain, lots of learning taking place. REM sleep linked to production of neurotransmitters and consolidation of memories. Supported by fact that premature babies spend 90% of time in active sleep.

• By age of 5 children EEG patterns look like those of adults. (Still sleeping 12 hours a day) 
• Have more REM (about 30% of total sleep time).
• Boys sleep longer than girls.
• In childhood it is common for children to experience parasomnias.

• During childhood need for sleep decreases, adolescence increases to about 9-10 hours/night.
• Circadian rhythm changes, teenagers feel more awake later at night and more difficulty getting up earlier. (Phase delay).
• REM sleep in males is sometimes accompanied by o----- and e----------, less likely at other ages.

• Adolescence:

Hormone changes — Hormones predominantly released at night, sleep patterns disturbed leading to deprivation. Correlates of sleep deprivation similar to those ‘typical’ of puberty.

Can also explain upset to the circadian clock, delayed phase syndrome. (Crowley et al, 2007). Researchers recommended school day begins later to accommodate poor attention spans of teens in the early morning (Wolfson and Carskadon, 2005).

• Adult sleep around 8 hours. 25% REM sleep.
• Parasomnias of childhood are more rare in adulthood, increasing frequency of other sleep disorders (insomnia, sleep apnoea).
• As get older total sleep time remains the same but older people more difficulty going to sleep and staying asleep. Nap to satisfy needs.
• Pattern of sleep changes, REM decreases to 20% of total sleep. 
• Slow wave sleep as little as 5% or even none. 
• NREM increases.
• Older people experience phase advance, feel sleepier early in the evening and waking up earlier.

• Adulthood:

Too much sleep may not be a good thing — Kripke et al. (2002) surveyed over one million adults, found that people sleeping for only six or seven hours had a reduced mortality risk, those sleeping eight horus had 15% increase in risk of death, risk over 30% for people sleeping more than 10 hours. 

(Correlational data, may be other intervening variables that cause link. Underlying illness may lead to increased sleep needs and increased mortality. 

• Old age:

Reduced sleep may not be the consequence of physiological changes — May be explained in terms of problems staying asleep e.g apnoea. Staying asleep explained as reduced SWS in old age. Older sleep more easily awoken. 

Poor sleep might explain old age — Reduced SWS leads to reduced production of growth hormone (mainly produced in SWS) may explain symptoms of old age e.g. lack of energy, lower bone density (Van Cauter et al, 2000).

IDA

Lifespan approach recognises sleep patterns are not consistent as we age. Psychologists used to ignore age-related changes and assumed one sleep pattern for all ages. Can now better understand effects of ageing.

Sleep behaviour conclusions mainly based on research conducted on American and British. 

Research assumes that there are no cultural and age differences. Research largely conducted on American and British samples. Tynjala et al. (1993) looked at sleep patterns in adolescents living in different cultures. 400,000 11-16 year olds from 11 European countries questioned. Results show significant differences. Important contributory factor number of evenings spent outside the home, young people went to bed later and had too little sleep.

In Korea mean sleep time about 6.5 hours of adolescents (Shin et al, 2003). A study in Iran found mean time of 7.7 hours (Ghanizadeh et al, 2008). Sleep duration influenced by cultural practices and reminds us that our view of behaviour often ignores such influences.

RWA

Teenagers start school later to accommodate delayed sleep phase syndrome. 

Effects of ageing could be reduced by improving sleep ‘hygiene’. Improving healthiness of sleep, e.g. resisting naps during the day in order to not decrease amount of deep sleep during the night