Sleep Facts-stages of sleep

I found this info on the Babywhisperer website and thought it might be helpful to my readers.  This explains the  various stages of sleep and  how children differ from adults in sleep and why young babies are such "noisy sleepers" as I call them:) It explains how young infants can startle and "jolt" themselves awake.  In years past, when children were laid on their tummies, these jolts weren't as pronounced because of their sleep position and it didn't bother them.  With the "Back to Sleep" campaign against SIDS (putting them to sleep on their backs instead of tummy), I noticed my second had an especially strong startle reflex and she had a hard time settling into deeper sleep.  Swaddling helped her immensely.  It also explains how it takes time for them to establish all the stages of sleep and why those first couple months can be rough.


STAGES OF SLEEP

Sleep is split into REM sleep (rapid eye movement sleep or dreamimg state) and Non-REM (quiet sleep). Non-REM sleep has 4 stages (3,4):-

A.Drowsiness
B.Light sleep
C.Transition between light and deeper sleep
D. Deep sleep
Then….
      REM sleep


Non-REM sleep
When a baby starts to fall asleep, they enter the first stage – drowsiness. You may be able to see their eyes may move slowly under the lids. They will become less focused on the stimuli around them (3). As babies try to transition through to the second stage you may notice them jolt or jerk or startle, which can wake them (2). Once they have entered the light stage of sleep, they can still be easily woken, and may experience another jolt as they are transitioning into the next stage. This is very common. Once in a deep sleep, it is very difficult to wake them and you may be able to pick them up without disturbing them. The heart beat is slow and breathing regular.
Deep sleep is restorative, and is thought to be a time when the immune system is boosted and healing and growth takes place (3,4)

REM sleep
During REM sleep babies are active and will use more energy. Although babies are very relaxed when in this state, you may see small twitches on the hands, legs or face. You will also see their eyes darting about under the lids. The heart beat and breathing may be irregular in young babies,  but this is normal. It is a time when learning is organised and stored. A full term, newborn baby will spend more than 50% of their sleep in REM, (2) and preemies 80% this decreases with age. In adults REM only accounts for 20% of sleep. Most of the arousals babies make from sleeping is after the REM stage, which explains why babies wake more often than adults and why preemies wake more often then full term babies. (2,3)

Sometimes they can be woken up easily in the this stage, but at other times it is very hard. It all depends on how important the noise they heard was to them, and how interesting or exciting the dream was! (2)


LENGTH OF SLEEP CYCLES

In babies the length of the average sleep cycle is about 45 mins, (1) this doubles to 90 minutes in adulthood. (3)


HOW SLEEP DEVELOPS
Sleep begins to develop while the baby is still in the womb. REM sleep appears in the unborn child of about 6-7 months gestation, and non-REM at 7-8 months gestation.
Non-REM sleep is not properly developed in the newborn baby. This happens between 1- 3 months, when the 4 stages, become established. Newborn babies will enter REM sleep straight away, when falling asleep. (1,4)

DAY & NIGHT TME SLEEP
The pattern of being awake during the day and asleep at night is called a ‘diurnal’ sleep pattern. Babies are not born with this. They come to us with a 24 hour clock and cannot distinguish between day and night (1). They need to have the physiological maturity, (4) plus your help and guidance to achieve the ability to stay awake for most of the day and sleep throughout the night. A good routine will help to establish this. (1)

Night time sleep is different than day time sleep.

Night
During the first couple of hours of night time sleep, babies enter a deep sleep, then for most of night, they cycle frequently between light sleep and REM with partial wakings after each REM period. (3) This is why, if they have not learned independent sleep, they wake a lot at night. Partial wakings become more frequent towards dawn.(2) The final part of the night time sleep cycle, finishes with about an hour of more deep sleep near to morning. If a baby wakes before finishing this last part of the cycle, going back off to sleep can be hard, as they have already slept for most of the night, so are already refreshed and do not have the motivation to return into that deep sleep, which is very important.

We start to fall asleep when our body temperature falls and the level of the hormone, cortisol falls. When the cortisol level rises in the morning, we wake.
If the cortisol levels are high, it is very difficult to fall asleep (3).

Day
During the day, sleep consists of naps, which vary in length. Each sleep cycle lasts approximately 45 minutes. These consist of the 4 stages of sleep, plus REM sleep. Once they have finished one 45 minute cycle they may enter another, and so the cycle is repeated, unlike the pattern of night time sleep.

References
(1)   Hogg, T. (2005) The Baby Whisperer Solves All Your Problems. London: Atria books
(2)   Carskadon, M.A. & Dement, W.C. 1989 as cited in Hames (2002) Help Your Baby To Sleep. London: NCT Publishing
(3)   Ferber, R. (1986) Solve Your Childs Sleep Problems. London: Dorling Kindersley Publishers Ltd
(4)   Hames, P. (2002) Help Your Baby To Sleep. London: Thorsons/NCT Publishing



N.B. Ferber's work has been used purely for factual information only. B.W. does not in anyway advocate or condone the methods he uses to achieve independent sleep.

« Last Edit: June 26, 2006, 12:01:52 PM by jaime-jaina&luke »