Dr Mark Butler and Dr Mike Farquhar
Sleep is a fundamental physiological function, but hardly features in most medical school curricula. Some knowledge about sleep is extremely useful for any paediatrician. This is the first in a series of articles, based around the teaching on sleep in the education programme at Evelina London Children’s Hospital. We’ll cover the basics of what any paediatrician should know about sleep, including the competencies specified in the RCPCH paediatric Progress curriculum.
Sleep is integral to physiological and neurocognitive function, hormone regulation, growth, learning, higher mental functions and more. Disruption of sleep quality is linked to multiple negative outcomes: poor academic performance, obesity, and increased risk and severity of chronic diseases.
Sleep problems in children are very common. Around 25% of parents report problems with their child’s sleep at some point. Sleep problems may be a primary reason for seeking medical advice, or may be raised during consultation about another issue. Sleep may not be raised spontaneously by young people or parents, but actually may be contributing significantly to the presentation.
A targeted sleep history is an enlightening part of a consultation with many children, the following three questions are suggested as a screening exercise in the excellent article by Jess Turnbull and Mike Farquhar “Fifteen-minute consultation on problems in the healthy child: sleep”.
Does your child have any difficulty getting to sleep or staying asleep?
Does your child do anything unusual in the night?
Is your child unusually sleepy in the daytime?
Phases of sleep
Sleep is classified into 3 or 4 stages (depending on how precise you wish to be). For a general paediatrician and for speaking to children and young people, it is probably most helpful to consider three phases; Light, Deep and REM sleep,
In an ideal situation, where you have a healthy sleep pattern you move through the various phases in a relatively predictable way. Where sleep is disturbed, or disrupted or sleep habits are poor then the phases of sleep can become much more chaotic, a fact which we will return to later.
This is a hypnogram showing a typical healthy night’s sleep for an adult. Though the details of sleep physiology change with aging this broad structure is consistent. After falling asleep you usually move relatively quickly into deep sleep and then cycle through the different phases, including wakefulness, with cycles lasting approximately 90 minutes. Understanding the phases of sleep is crucial to understanding how sleep problems may arise.
Light sleep includes what is referred to as Non-REM stage 1 and 2 sleep. In stage 1 sleep you are only very lightly asleep, it lasts a short time and if you are awoken during this time you may not feel as though you have slept at all. You start to prepare physiologically for sleep, you move less, your heart rate and breathing slow. EEG recording at this time starts to show the signs of sleep, theta waves appear and alpha waves recede.
In stage 2 non-REM sleep you start to move into deeper sleep and it becomes more difficult to wake you. Your heart rate, blood pressure and body temperature fall further, brainwave activity continues to slow and EEG recording during this phase shows ‘sleep spindles’, spikes of rapid activity which are thought to be related to formation and integration of memory.
In Deep Sleep (also referred to as non-REM stage 3) your muscles relax, your metabolism, heart rate and breathing slow, your temperature and blood pressure drop. This phase of sleep is physiologically restorative. If you are sleep deprived and tired you will tend to move more rapidly into non-REM sleep. EEG shows characteristic slow high amplitude delta waves. Dreaming may occur during this stage, though these dreams are usually less vivid and more disjointed than those that occur in REM sleep.
REM sleep is ‘dream sleep’. Brainwave activity during this phase of sleep looks very much like an awake brain. Rapid side to side movements of the eyes occur during this phase. Most dreams take place during this phase and the dreams are most vivid. Your heart rate and respiration are similar to waking, physiologically this stage of sleep most like waking. We are immobilised by ‘REM atonia’ a dissociation of the skeletal muscles from conscious control which stops us from acting out our dream activity.
How you feel on waking is related to the stage of sleep you wake from. If you wake naturally, as the person in the above hypnogram does just before 7am, you would feel both mentally and physically refreshed and alert. If you are woken prematurely, by an alarm or other external stimulus, from a deep sleep you are likely to feel disorientated, grumpy and slow, you may physically be recovered (depending on how long you have slept) but you may take a while to get up to speed mentally, as all of us who have woken up their consultant at 3am can attest.
What is ‘normal’?
Detailed objective measurements of sleep are complex and available in only specialist centres, but simple history from the child and carers (and anyone they share a room with) can give you a lot of information. It is also worth remembering that you will usually be to an extent assessing and managing the subjective experience.
Quantity of sleep
If someone asked you how tall should a child be, you would quite rightly reply “it depends..” like any physiological variable, there is a great deal of individual variation around a normal distribution. Age is an important factor, this graphic from the National Sleep Foundation gives you an indication of normal ranges across different age groups, but is it important to consider each child individually.
It’s not unusual for children we see to be sleep deprived to some extent, identifying the factors contributing to this is big step in the right direction, and allows families to start taking action. See ‘Good Sleep’ below for advice on starting to improve sleep habits.
Waking during the night
Waking during the night is normal, though we usually are not aware of it in the morning. This is a brief period of wakefulness where we subconsciously check our surroundings, ensure that all is as it was when we went to sleep, we are not about to be eaten by lions etc., and then return to sleep. Children who are reliant on certain situations or behaviours, for example an infant who ‘expects’ to fall asleep on their parent following a feed, will not be able to resume sleep so easily. Similarly, a child that falls asleep in one situation, but is then moved while asleep will tend to wake, be confused by their apparent sudden change in surroundings and will be more likely to rouse and become distressed. These episodes of night time waking can be incredibly stressful for parents, simply understanding why this occurs goes a long way towards helping people to improve their child’s (and their own) sleep.
Difficulty falling asleep
Children will usually fall asleep within 30 minutes of going to bed, delays beyond 30-45 minutes should be evaluated. Careful history taking should help establish contributing factors, which may be physical e.g. poorly controlled eczema and itch, psychological e.g. anxiety, or behavioural e.g. reliance on falling asleep while being cradled or held. Often a combination of several factors are involved. Trying to go to sleep at the ‘wrong’ time can also make falling asleep difficult.
Alertness and sleepiness are influenced by many factors. A simplified but useful way to think about this is illustrated in the graph below. As soon as we wake, our need for sleep begins to increase. Our urge sleep is governed primarily by our circadian rhythm there is a peak in the early afternoon, (siesta time) and then a gradual increase again through the later part of the day. Most people experience an increase in alertness in the evening about 90 minutes before their optimal bedtime. Trying to go to sleep during that period of alertness is usually counterproductive, you lie awake, become frustrated and then struggle with initiating sleep.
To achieve high quality and restful sleep, good sleep habits are essential. Some advice is age specific, but the general principles hold for all of us.
- Consistency is the foundation of good sleep habits, set an age appropriate bedtime and stick to it. Try and wake up at the same time too. Try not vary more than hour on weekdays/ weekends/ holidays.
- Establish a clear routine (for example; pyjamas, story, brush teeth, toilet, bed)
- Ensure they are not thirsty or hungry, a drink and light snack can be an important part of the routine for many children
- A bath can be a good part of this routine too, but this does not work for every child, if baths are a fight (or too exciting) this will not be helpful.
- Turn screens off at least an hour before bed, keep screens out of children’s bedrooms (‘blue light reduction’ modes on phones are not effective)
- A quiet, relaxing activity will help children start to ‘wind down’ in preparation for sleep (reading, colouring-in, building, jigsaws etc.)
- Ensure the environment is favourable for sleep, comfortable, cool, dark, quiet and not too stimulating or cluttered (some children will not like complete darkness, a nightlight is fine)
- Exercise and get outside in daylight, especially in the morning to help strengthen your circadian rhythm
- As much as possible the bed and bedroom should be just for sleep. Avoid using as a punishment
- Avoid caffeine and other stimulants
Daytime sleep is normal for infants and younger children. Most children will have stopped requiring a nap by school age. A school age or older child who wants to sleep during the day warrants further sleep evaluation.
We all recognise a sleepless night or severe jet lag can make us feel awful, but we may not recognise the impact that poor-quality or inadequate sleep may have on us. As well as the obvious tiredness and lethargy, irritability, poor concentration and loss of focus, people may experience a variety of somatic symptoms, headaches, musculoskeletal and GI symptoms, and many medical conditions are worsened by a lack of sleep. Anxiety in particular is often deeply entwined with sleep problems and each will impact the other.
In addition, there is evidence linking sleep to many negative outcomes; poor academic performance, behavioural issues, obesity, depression, immune function, heart disease and much more.
Unfortunately, children may have hypnograms that look more like this than the previous example. Sleep is fragmented and irregular, although the cycles we saw previously are still broadly evident, the pattern of movement between them is chaotic. To a casual observer the child might seem to have slept for a reasonable period, but the quality of the sleep is poor, and the child (and family) will experience the consequences of that.
Many of the reasons for sleep disruption will be those mentioned in the list above. A child without a consistent routine, in an unsuitable environment, doing the things that they shouldn’t, will not sleep well. Other factors may also contribute, in addition to sleep specific issues like obstructive sleep apnoea, many medical conditions will disrupt sleep; pain, itch, coughing all being very common examples. Psychological, behavioural, social and emotional issues are also very important.
A consistent routine is the foundation of developing good sleep, the tactics in the ‘good sleep’ section above are very effective in improving sleep in most children, though change will take time. Children will require an approach targeted to their own particular needs, but this list is a very good place to start. The behavioural aspects of sleep should not be underestimated. Our article on behavioural issues in children has some further tips.
Our next article will look at some sleep phenomenon which can be a source of great anxiety to parents and professionals including, nightmares, night terrors, sleepwalking and head banging. We will see why understanding a little about the phases of sleep helps understand these experiences.
Sleep is important!
Disrupted sleep has a wide-ranging impact on health and wellbeing
Many factors may contribute to poor sleep, every child will need an individualised approach.
The basic steps to good sleep are simple and will help many children (and adults!)
Dr Mark Butler, consultant general paediatrician, and Dr Mike Farquhar, consultant in Sleep Medicine, Evelina Children’s Hospital, London
Turnbull JR, Farquhar M Fifteen-minute consultation on problems in the healthy child: sleep Archives of Disease in Childhood – Education and Practice 2016;101:175-180. (Free)
The Evelina Children’s Hospital Sleep Medicine Service has produced a free children’s sleep app, Kids Sleep Dr, (only for iOS) – a sleep diary app for parents to track their child’s sleep and receive personalised sleep tips.