Sleep

How common is sleep disturbance in Smith-Magenis syndrome?

Almost all children and adults with Smith-Magenis syndrome have sleep difficulties, including difficulties with waking up in the night, early waking and daytime sleepiness.

A recent meta-analysis by Agar and colleagues looked at all available data and found that overall rates of sleep problems in Smith-Magenis varied from 44-77%. These estimates were higher for ‘general’ sleep problems than for specific types of sleep disorders, such as sleep-related breathing difficulties. However, rates did vary depending on the type of sleep problem measured and the tool used to measure it.

How is sleep disturbance measured?

Sleep disturbance has been measured in Smith-Magenis syndrome using a technique called ‘polysomnography’.  Polysomnography is a way of recording a person’s body functions as they sleep.  Brain waves, heart rate, levels of oxygen in blood, breathing, eye-movements and leg movements are recorded. More recently, researchers have been able to measure sleep in children with Smith-Magenis syndrome using wearable devices. These devices measure light and movement which can be used to analyse when a person is awake or asleep. From this we can calculate key sleep ‘parameters’ such as the total sleep time, time taken to fall asleep and amount of time spent awake overnight. Many studies also use sleep diaries and questionnaires to measure sleep disturbance in SMS.

What does sleep disturbance in Smith-Magenis syndrome look like?

Sleep difficulties are believed to begin in childhood and carry on into adulthood, with some changes over time.

Infancy:  Reduced 24 hour sleep is reported despite parental beliefs that their children are good sleepers.

Childhood: Night-time and early morning waking, with shortened sleep cycles are noted.  Daytime fatigue is noted.

Older children, adolescents and adults: Activity appears to be elevated early in the night suggesting it is more difficult for children to get to sleep.  Increased age has been linked to reduced night-time sleep but increased shorter naps.

Some parents and carers have reported decreases in sleep problems as individuals with Smith-Magenis syndrome get older.  This may be because of reduced disruptive night-time behaviour rather than improved sleep. A recent longitudinal study by Agar and colleagues found that key sleep parameters remained stable over three years in a sample of 12 children with Smith-Magenis syndrome.

What are the causes of sleep difficulties in Smith-Magenis syndrome?

Sleep difficulties have been linked to an advanced melatonin release pattern which disrupts the sleep-wake cycle.  This leads to too much melatonin being released during the day and not enough at night. Melatonin is a hormone released in the body in response to darkness which regulates sleep-wake patterns.

It is hypothesised that this difference in Smith-Magenis syndrome is underpinned by problems with the regulatory function of the pineal gland in the brain. This has been linked to changes to the RAI1 gene.

This is the opposite pattern to the majority of people and leads to day-time sleepiness and night-time waking.

Another potential cause of sleep difficulties in Smith-Magenis syndrome is midface hypoplasia.   Midface hypoplasia (the slower development of the centre of the face) causes obstructive sleep apnoea (when normal breathing is interrupted by a blockage of air flow) which consequently may affect the individual’s sleep quality.   This possibility needs to be excluded as a cause of sleep problems especially in young children and can be treated with an adenoidectomy (removal of small lumps of tissue at the back of the nose).
Poor sleep may also be linked to pain which can cause or prolong overnight waking.

What is the relationship between behaviours that challenge and sleep?

Daytime sleepiness may account for some of the difficult behaviours shown by people with Smith-Magenis syndrome. This is supported by research that has found a link between temper outbursts and increased melatonin in the body.

Some behavioural problems associated with Smith-Magenis syndrome (e.g. hyperactivity, attention deficit and behaviours that challenge ) may be underpinned by fatigue.

How can sleep difficulties be managed?

Medication that provides melatonin in the evening in combination with medication that suppresses daytime release has been linked to sleep improvements for children with genetic disorders generally.

There is some evidence that even severe sleep problems in Smith-Magenis syndrome can be improved with melatonin; however, the evidence from research studies is inconsistent.

A series of studies have suggested that the combination of acebutolol (a beta-blocker) and melatonin may improve sleep in children with Smith-Magenis syndrome, including increasing total sleep time and reducing early morning waking. Reports have also indicated reductions in hyperactivity and improvements in cognitive performance.

However, some researchers advise that the findings should be interpreted with caution until further studies are conducted. They note that, aside from the reported reductions in temper outbursts, specific measures for behavioural improvements were not clearly outlined in the research. Additionally, while sleep aids, particularly melatonin, are commonly prescribed and often initiated early in treatment, some studies suggest that their use may not significantly influence caregiver assessments of disruptive behaviours or sleep parameters.

For more information on the nature of sleep in children with intellectual disability, and what can be done to reduce or improve sleep problems, click here to read Cerebra’s guide.

If you want help and advice on sleep issues in Smith-Magenis syndrome click here.