Lifespan Changes in Sleep
> Babies sleep a lot more than children & adults, and also have different sleep patterns & stages of sleep - tend to sleep about 16 hours a day but not continuously.
> Babies usually wake up every hour or so because their sleep cycles are shorter than the adult 90 minute cycle - infants have sleep stages which are similar to adult sleep, called quiet sleep & active sleep (immature versions of SWS and REM).
> At birth there's more active sleep than adult REM sleep; about half of infant sleep is spent in active sleep.
> Adults can usually go fairly directly into the state of deep sleep (quiet sleep) whereas infants in the early months enter sleep through the initial period of light sleep & after 20 minutes they gradually enter deep sleep.
> By the age of 6 months a circadian rhythm has become established (1 main sleep-wake cycle) & by the age of 1 year infants are usually sleeping mainly at night, with 1 or 2 naps during the day.
> The periods of deep sleep lengthen and there's a reduction in the amounts of active/REM sleep - it's not known if REM activity is accompanied by dreaming as babies & children are too young to provide reliable subjective reports.
> By the age of 5, children have EEG patterns that look like those of an adult but they are still sleeping more (about 12 hours per day) & having more REM activity (about 30% of total sleep time).
> Boys sleep slightly more than girls.
> During childhood it's not uncommon for children to experience a variety of parasomnias (sleep disorders such as sleep walking or night terrors).
> During childhood the need to sleep decreases, but in adolescence it increases slightly, to about nine or ten hours a night.
> Circadian rhythms also change so that teenagers feel naturally more awake later at night and have more difficulty getting up early (a phase delay).
Adulthood and old age
> 'Normal' adult sleep is about eight hours per night, with 25% in REM sleep - childhood parasomnias (sleep walking) are more rare in adulthood but there's an increasing frequency of other sleep disorders (insomnia & apnoea).
> With increasing age, total sleep time stays about the same but older people have more difficulty going to sleep & wake up more frequently (up to 6 times a night) - may have to nap during the day to satisfy their sleep needs.
> With old age the pattern of sleep changes; REM sleep decreases to about 20% of total sleep time & the amount of slow wave sleep is considerably reduced to as little as 5% or even none (other kinds of NREM sleep increase).
> Older people also experience a phase advance…