What are sleep disorders?

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Every single person experiences trouble sleeping at some time or another. This could be temporary, such as when the neighbours are having a party, or because you’re nervous about a job interview.

A temporary sleep disruption usually has a discernible cause, and the sleep disruption comes to an end once that particular source of stress or noise is no longer present.

If you constantly feel sleepy during the day, you have difficulty falling or staying asleep at night, you wake up very early, or feel tired when you wake up, you could be suffering from a more serious sleep disorder. You may have had this problem for a long time, so it could start feeling normal to you.

Sleep disorders refer to disturbances that occur within sleep, or in your sleep cycle, that results in daytime consequences and disturbances in occupational and/or social functioning. In other words, these are abnormalities of sleep physiology that have negative consequences. 

Furthermore, these negative consequences have to be sustained for a period of time. For example, if you have insomnia symptoms for 2 or 3 days, it doesn’t constitute a disorder. For insomnia to be considered a disorder, you need to experience insomnia symptoms on most nights for a month.    

It’s estimated that one in four people suffer from some form of sleep disorder that affects both their productivity and quality of life. 

The most common sleep disorders are:

  • Insomnia
  • Obstructive sleep apnoea (OSA)
  • Parasomnias such as sleepwalking, sleep terror disorder, and REM sleep behaviour disorder (RBD)
  • Restless legs syndrome (RLS)
  • Narcolepsy and other hypersomnias (disorders of excessive daytime sleepiness)
  • Circadian rhythm disorders – these are disorders of the sleep-wake cycle, for example jet lag and shift-work sleep disorder.


Insomnia refers to the inability to fall sleep, the inability to maintain sleep, or waking up early and not getting enough sleep. While occasional insomnia as a symptom is very common, insomnia disorder is a medically classifiable condition.

It requires the above-mentioned symptoms to be associated with impaired functioning during the day, and symptoms should last for more than one month. 

Insomnia is the most common sleep disorder. The International Classification of Sleep Disorders (ICSD-3) defines insomnia disorder as follows: “Insomnia is a persistent difficulty with sleep initiation, duration, consolidation, or quality that occurs despite adequate opportunity and circumstances for sleep, and results in some form of daytime impairment.

When no underlying cause can be found, a person is said to be suffering from primary insomnia. Where a cause is found (for example, a medical condition), it’s classified as secondary insomnia.

People with insomnia may experience loss of energy and enthusiasm, have problems with memory and concentration, and may feel ill, sleepy and frustrated. Poor sleep can be associated with accidents and lower work productivity, and may worsen medical and psychological conditions.

These consequences make insomnia an important health problem that deserves serious attention.

Insomnia typically involves the following symptoms:

  • Difficulty falling asleep and/or maintaining sleep and/or waking up too early.
  • Waking up feeling unrefreshed or drowsy. 
  • In more severe cases of insomnia, you may feel fatigued, depressed, anxious or irritable.
  • People with insomnia often suffer from daytime sleepiness, fatigue, forgetfulness and trouble concentrating.
  • Insomnia may arise suddenly (acute) or gradually (chronic). In acute insomnia, there’s usually a triggering factor that can be identified. Examples include separation, bereavement, change in sleep schedule, or an increase in your daily stress levels. By definition, acute insomnia is short-lived and can usually be easily managed by a short course of sleeping tablets and counselling addressing the triggering factors.
  • Chronic insomnia has a more insidious onset over a period of time. Its course can be situational, recurrent or persistent. 

IMPORTANT: The earlier you seek help for insomnia, the better the clinical outcome. 

There are 8 different types of insomnia

1. Insomnia due to a drug or substance is related to the use of any of the following substances, but it can also occur when you stop using the substance:

  • Alcohol
  • A food item
  • Medication
  • Caffeine

2. Behavioural insomnia of childhood occurs when children don't have a relatively specific bedtime. If children aren’t given consistent bedtimes, they may linger awake for hours at night and set a behavioural pattern that could last.

3. Adjustment insomnia is also called short-term or acute insomnia, and usually stems from stress. The insomnia should end when the source of stress is gone or with adaptation to the stress. This stress isn’t always as a result of a negative experience – it can be a result of something exciting or just a big change.

4. Insomnia due to a medical condition is a symptom of a mental health disorder. The course and severity of insomnia are directly linked to that of the mental health disorder, but this insomnia is considered a disorder only if it’s severe enough to require separate treatment.

5. Idiopathic insomnia has no identifiable cause, i.e. it isn’t the result of any of the following:

  • Other sleep disorders
  • Medical problems
  • Psychiatric disorders
  • Stressful events
  • Medication use
  • Other behaviours

This insomnia may result from an imbalance in your body, such as an underactive sleep system and/or an overactive awakening system, but the true cause of the disorder is still unclear.

6. Organic, unspecified insomnia is caused by substance exposure, a medical disorder or a physical condition, but the specific cause remains unclear. Further testing is required (this name may be used on a temporary basis while further testing and evaluation are conducted).

7. Psychophysiological insomnia is associated with excessive worrying, specifically focused on not being able to sleep. The disorder may start suddenly following an event, or develop slowly over many years.

People with this sleep disorder worry excessively about their insomnia and about being tired the next day, resulting in tension and anxiety as bedtime approaches. They may have racing thoughts that all relate to insomnia and trying to fall asleep, which makes falling asleep less likely.

8. Paradoxical insomnia is a complaint of severe insomnia. It occurs without objective evidence of any sleep disturbance. People with this disorder often report little or no sleep for one or more nights.

They also describe having an intense awareness of the external environment or internal processes consistent with being awake, suggestive of a state of hyper-arousal. A key feature is an overestimation of the time it takes them to fall asleep. They also underestimate their total sleep time.

The gold-standard, evidence-based treatment for insomnia that is uncomplicated by a medical or psychiatric condition (also called ‘primary insomnia’) is cognitive behavioural therapy for insomnia (CBT-I).

CBT-I utilises the following techniques and interventions to help the individual restore their normal (physiological) sleep: 

  • Sleep hygiene (good sleep habits)
  • Relaxation therapy
  • Stimulus control
  • Sleep restriction
  • Cognitive therapy (addressing negative automatic thoughts)
  • Behavioural adjustments

Where the sleep-loss effects are having significant daytime consequences, a short course of sleeping medication may be useful to help restore sleep loss and reset your sleep cycle.  


Obstructive sleep apnoea (OSA)

If you believe snoring isn’t dangerous, think again. In some cases, it’s a symptom of sleep apnoea, which can be life-threatening.

Sleep apnoea (when you stop breathing for short periods while sleeping) is one of the most undiagnosed medical conditions. If you sleep badly, snore heavily and are overweight, you should consult your doctor.

Sleep apnoea is a sleep disorder that’s characterised by cessation or interruptions of breathing during sleep, resulting in oxygen deprivation and fragmentation of sleep.  

There are three types of sleep apnoea:

  • Obstructive sleep apnoea (OSA): this is the most common type. It occurs due to an obstruction or weakness in the airway that results in obstruction of airflow to the lungs sleep. Each obstruction needs to last a minimum of 10 seconds for it to be classified as abnormal. The collapse or narrowing of the upper airway may be a result of several factors including inherent physical characteristics, excess weight, and alcohol consumption before going to bed.
  • Central sleep apnoea: this is caused by a delay in the signal transmitted from the brain to elicit breathing and is usually part of a brain or cardiac disorder such as following a Stroke or Cardiac Failure. 
  • Mixed sleep apnoea: As the name suggests, it’s more or less a mixture of the above. It occurs less frequently than obstructive sleep apnoea, but more frequently than central sleep apnoea.

Many people joke about being kept awake by their partner’s snoring. But sleep apnoea, if left untreated, can be lethal over time. It can cause serious diseases such as diabetes, kidney damage and depression, and it may lead to a heart attack.

If you or someone you know snores regularly during sleep, is overweight and experiences daytime tiredness, see a sleep specialist. The South African Society of Sleep Medicine has a full list of all sleep specialists in South Africa.


Parasomnias are sleep disorders that are characterised by abnormal behaviour arising from sleep.

They’re classified according to the sleep stage from which they occur:

  • Non-REM sleep parasomnias
  • REM sleep parasomnias

Non-REM sleep parasomnias (also called disorders of arousal)

These occur during non-REM (or slow-wave / deep) sleep, usually within the first 2 hours of falling asleep (this is when we have the bulk of our non-REM sleep).

Examples of non-REM parasomnias are: 

  • Sleepwalking disorder
  • Sleep terror disorder
  • Confusional arousals

Sleepwalking, sleep terrors and confusional arousals (i.e. disorders of arousal or DOA) are relatively common sleep disorders reported to occur in as many as 20% of children, and between 2% and 4% of adults. As is the case with many sleep disorders, disorders of arousal don’t occur spontaneously. Instead, they’re thought to be the result of several interacting factors in genetically susceptible people.

A sleepwalking episode occurs characteristically in the first period of deep sleep, usually within an hour to two hours of falling asleep.  

Sleepwalking runs in families and has a genetic basis. Sleepwalking usually appears in childhood, continues through adolescence, and often stops in adulthood. Rarely, it can appear for the first time in adulthood. 

The behaviour in a sleepwalking episode can be extremely variable and may be very complex. It can vary from sitting up in bed, hitting or trying to strangle your partner, to getting up and wandering around the room. In very complex episodes, some sleepwalkers exit their houses and even drive their cars. 

Sleepwalking occurs during an unusual brain state in which higher cognitive (so-called executive functions) are limited or absent, i.e. there’s no active consciousness. Classically, most sleepwalking episodes last a few minutes and usually consist of wandering around the house.

It often involves urinating in cupboards with the sleepwalker frequently returning to bed. In cases where severe violence has been reported during sleepwalking, the episode may last up to an hour. There’s usually no memory of the episode on waking. 

Sleepwalking and related disorders are, like most medical conditions, the result of factors that predispose, prime (or provoke), and those that precipitate (or trigger) episodes. In the absence of one or more of these factors, sleepwalking is thought to be less likely to occur.  

  • Predisposition to sleepwalking is based on genetic susceptibility and has a familial pattern.
  • Priming (or provoking) factors include conditions and substances that increase slow wave sleep (SWS), or which make arousal from sleep more difficult. By increasing slow wave sleep, a predisposed sleepwalker is more susceptible to sleepwalking. It’s generally accepted that factors that deepen sleep, fragment sleep and/or make arousal from sleep more difficult increase the chances of sleepwalking and similar disorders in those individuals who are genetically predisposed. These factors include sleep deprivation, use of alcohol, use of medication and fever, among others. In addition, stress and stressful life events have also been associated with sleepwalking.
  • Precipitating factors (or triggers) are important in the context of the presence of the above predisposing and priming factors to activate the sleepwalking episode. In other words, unless something “goes bump in the night”, it’s unlikely that a sleepwalking episode will occur. The event that triggers the episode may be an “internal factor” such as sleep disordered breathing (e.g. snoring, sleep apnoea), restless legs, or periodic limb movements (PLMD). Alternatively, it can be an “external factor” such as a loud noise, or being touched or pushed while in deep sleep.

Restless leg syndrome (RLS)

Restless leg syndrome runs in families. It’s characterised by an unpleasant itching, prickling or tingling in the legs or feet that’s relieved by moving around. Women are most often affected. It causes sleeplessness and is also linked to anaemia, pregnancy and diabetes. Medicine specifically targeting the neurotransmitter dopamine is effective in treating it.

If you score positively on two or more of the following questions,you should see a sleep specialist:

  • Do you have, or have you ever had, an urge to move the legs, usually accompanied or caused by uncomfortable and unpleasant sensations in the legs?
  • Do you have, or have you ever had, the urge to move or unpleasant sensations in the legs that begin or worsen during periods of rest or inactivity, such as lying down or sitting?
  • Do you have, or have you ever had, an urge to move or unpleasant sensations in the legs that are partially or totally relieved by movement, such as walking or stretching, for at least as long as the activity continues?
  • Do you have, or have you ever had, an urge to move or unpleasant sensations in the legs that are worse during the evening or night than they are during the day, or that only occur during the evening or night?

Periodic limb movement disorder (PLMD)

Have you ever been woken in the middle of the night because your bed mate suddenly pulls up both legs, moves his feet, or throws his arms and legs wide? This is tell-tale behaviour of someone suffering from PLMD. It’s the only movement disorder that occurs only during sleep. It can vary from repetitive cramps or jerking of the knees, ankles and toes to large movements of all four limbs. 

Many people who have PLMD don’t realise their legs and feet move suddenly at night and disrupt their sleep. They just feel tired the next day. The occurrence of PLMD increases with age: almost 50% of people over 65 have it. Treatment with dopamine or sleeping pills can help. Up to 70% of people with restless leg syndrom have PLMD.


Narcolepsy is a disabling neurological disorder of sleep regulation that affects the control of sleep and wakefulness. It’s a lifelong disorder that affects 1 out of 2,000 persons worldwide. In Japan, it’s thought to be much more common, affecting 1 in 600 people.

For most individuals, symptoms present in the late teenage years or early twenties (typically before the age of 25). There are no differences in rates of narcolepsy among men and women. Narcolepsy is caused by a deficiency of a hormone called hypocretin (also called orexin), which is found in the hypothalamus and which functions as a regulator of sleep and wakefulness.

A reduction of orexin, or a deficiency of the hormone, causes the typical symptoms of narcolepsy:

  • Excessive daytime sleepiness 
  • Sleep paralysis
  • Hypnogogic hallucinations (the person may hear sounds that are not there and see visual hallucinations)

Where an individual is totally deficient of orexin, they develop the most disabling symptom of narcolepsy: cataplexy. This is the sudden loss of muscle tone in response to emotional stimuli.

REM behaviour disorder

REM behaviour disorder develops when the brain fails to temporarily paralyse the muscles during REM sleep. The result is that you literally act out your dreams. One doctor tells of a patient who knocked herself unconscious by running into a wall at the sleep clinic because she was “trying to catch a ball”. 

It’s rare, but seeing it is scary and sufferers can seriously injure themselves or others. In America there have been controversial cases in which sufferers have committed murder or other violent acts because of the disorder. Doctors link it with conditions such as Parkinson’s disease and brain-stem damage.

Read more:
Symptoms of sleep disorders

Reviewed by Dr Irshaad Ebrahim, specialist neuropsychiatrist in sleep disorders at The London Sleep Centre and The Constantia Sleep Centre. FRCPsych. April 2018.

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