Sleep has evolved to be an ‘all or nothing’ phenomenon but sleep disorders occur when there is a problem with transition from one state to another. They can be categorised as not sleeping enough (insomnia), being excessively sleepy (hypersomnia) or undesired events or experiences accompanying sleep (parasomnias). Sleep can also be disrupted by other things, such as movement problems at night – or by breathing difficulties (sleep apnoea).
Sleepwalking occurs during deep sleep, usually in the first part of the night and is nothing to do with dreams. For most people it is harmless, but it can be especially dangerous (or embarrassing) when staying away from home, or where the individual leaves the house. It is not dangerous to sleepwalkers to wake them but, like anyone else, they may respond with hostility on being woken from deep sleep. Stress does not cause sleepwalking, but it will make an episode more likely for someone who sleepwalks.
Sleep terrors (or night terrors) are different from nightmares, being a partial arousal from deep sleep where the person feels intense fear and may call out or even bolt from the bed. If the individual wakes completely they will have no memory of what happened. Night terrors are more common in children, most of whom “grow out of them”. They tend to occur earlier in the night.
Nightmares are frightening dreams which, like other dreams, have a narrative but, typically, there is a treat to life (one’s own, or loved ones’) or a serious threat to livelihood or reputation. People tend to wake from nightmares and have some recall. Recurrent nightmares may be a feature of post-traumatic stress, for which treatment is advised.
REM Behaviour Disorder
REM behaviour disorder is a condition that is often confused with sleepwalking. Normally, in rapid eye movement sleep (REM) the body is paralysed, which prevents us acting out dreams. In REM behaviour disorder, which is not common, the mechanism fails and the individual can act out a dream: this can be dangerous and medical assessment is important.
Sleep paralysis is relatively a common phenomenon where someone wakes and is unable to move and might feel a heavy pressure on their chest making it difficult to breath. This is where the paralysis of REM sleep persists for a short period after waking. Although it is a frightening experience, sleep paralysis is harmless. It can be more likely if someone fails to maintain a regular sleep pattern.
Narcolepsy is a rare condition that can be very disabling. It is thought to be caused by the faulty control of the sleep/wake mechanism, especially REM sleep, and there is evidence that it might be linked to a lack of the brain chemical that promotes alertness. People with narcolepsy have uncontrollable sleep attacks and often have cataplexy where there is a sudden loss of muscle tone (as occurs in REM sleep), often associated with surprise, excitement or laughter. Night-time sleep is often compromised.
Obstructive sleep apnoea and periodic limb movement disorder can each cause daytime sleepiness
Restless leg syndrome (RLS)
RLS causes you to have an irresistible urge to move your legs when you feel sensations of pain, tingling, itching, or prickling, (often described in terms like ‘ants crawling under the skin’). The discomfort is only relieved by moving the legs, but the sensations return when the legs are still again. RLS can be a symptom of anaemia, or a result of, iron deficiency or folic acid deficiency. Some pregnant women suffer from the condition, especially in the last trimester of pregnancy. Symptoms may also result from other conditions. If you suspect that you have RLS you should see your doctor
Periodic limb movement disorder (PLMD)
Periodic limb movement disorder is where the you repeatedly make kicking and jerking movements during sleep, most commonly with your legs or less frequently your arms. You are usually unaware that this occurs. If the movements cause momentary arousals, your sleep will be impaired, and you may experience daytime sleepiness. If the movements do not cause awakenings, it is more of a problem for a partner. Should you or your partner suspect periodic limb movements we would recommend seeking medical advice
Sometimes when drifting into light sleep you might experience a sudden involuntary movement, which might be associated with a falling sensation. This experience is known as a hypnic jerk. It is not entirely certain why they occur but, although they can be irritating, they are harmless.
Other causes of sleep disruption
One of the main causes of sleep impairment as we get older, besides those associated with natural ageing, is nocturia, the need to go to the bathroom multiple times during the night. Frequent nocturnal awakenings and the resultant sleep disturbance associated with nocturia can result in a severe disturbance of sleep leading to daytime fatigue and sleepiness together with a decrease in cognitive functioning and alertness.
While the sleep disturbance of the person with nocturia is of primary importance, it should also be recognised, that the sleep of the bed partner can also be greatly disturbed as a result of the sufferer having to get out of bed and go to the bathroom.
Approximately 10% of the general population over the age of 20 has nocturia and this increases with age. In the 50-59 age group, 58% of men and 66% of women experience nocturia.
Bruxism (Teeth grinding or clenching)
The repeated grinding of the teeth disrupts the sleep of both the sufferer and their bed partner. Bruxism affects about 1 in 12 people and is most common in people with sleep apnoea. It can cause severe damage to the teeth to such an extent that teeth are sometime lost and it can cause headaches and muscle aches. Lifestyles can also contribute to this disorder as heavy drinkers, smokers and coffee drinkers may be more prone than others. Individuals should look after their well-being as modifications to diet may help alleviate symptoms. In severe cases the use of a plastic splint or tooth guard to protect and preserve the teeth may be necessary during the night.