Infancy, at 6 months a circadian rhythm has been established, and by the age of one year infants are usually sleeping at night with fewer naps during the day. The period of deep sleep lengths and active/REM sleep shortens. It is not know whether REM sleep in babies means dreaming as babies and infants are not reliable subjective reports. Although active/REM sleep decreases in infancy there is still a lot of it compaired to an adult this may be because a lot of learning is taking place. Also during active/REM sleep neurotransmitters are produced with are needed for growth and development of the infant.
By the age of 5 EEG patterns look like those of an adults, although they are getting more REM sleep than an adult with 30% of sleep still spend in it REM sleep. Also a child sleeps longer than an adult about 12 hours. Boys sleep less than girls. In childhood it is the time when people are most likely to experience parasomnias.
Adolescence, during childhood the need for sleep decreases but in adolescence it increases to about 9 to 10 hours. Also adolescents go to bed later and find it difficult getting up (phase delay). The change in sleep patterns in adolescents may be linked to the change in hormone levels. These hormones are primarily received at night and therefore sleep patterns are disturbed leading to sleep deprivation.
By adulthood ‘normal’ sleep is about 8 hours per night. Parasomnias are less likely to develop but there is more chance of developing other disorders such as narcolepsy and insomnia. In adulthood there is a misconception that a good night’s sleep leads to good health, however studies have found that there is a link between higher mortality risk and too much sleep. Kripke et al., 2002 studied over 1 million adult men and women and found that people sleeping for 6 – 7 hours had reduced mortality risk, whereas those sleeping for an average of 8 hours had a 15% increase risk of death and an increase of 30% of death for people sleeping 10 or more hours. However, this research is correlations so there may be individual differences for example a person that sleeps more is more likely to be lazy and does less exercise so they would be less health so this would explain the findings.
With increased age, total sleep remains about the same, though older people have more difficultly going to sleep and wake up more frequently in the night in the night around 6 times. This means that they may have a nap during the day. REM sleep decreases to about 20% of overall sleep. SWS decreases to 5% or even non in some people. And other NREM sleep increases. Reduced sleep in old age is mainly the consequence of physiological changes in the body but may be explain in terms of actual problems staying a sleep, such as sleep apnoea or medical illness. Also problems with staying asleep are associated with the reduction in SWS so people have less deep sleep meaning that they are more easily woken.
Lifespan changes in sleep has useful applications of this research in ways to reduce the effects of ageing by improving sleep ‘hygiene’.
