Rapid-eye-movement is a stage during SLEEP in which the eyes are seen to move rapidly beneath the lids and during which dreaming occurs. It occurs for several minutes at a time approximately every 100 minutes.
Non-rapid-eye-movement (NREM) sleep This is subdivided into four stages, of which stage 1 is the lightest and stage 4 the deepest. The activity of the cerebral cortex (see BRAIN) is diminished and the body’s functions are mainly regulated by brain-stem activity. The metabolic rate is reduced; in keeping with this the temperature falls, respiration is reduced, cardiac output, heart rate, and blood pressure fall, and activity of the sympathetic nervous system is reduced. NREM sleep normally occurs at the onset of sleep except in neonates. During adult life, the duration – particularly of stages 3 and 4 – of NREM sleep becomes less, and very little of this deep sleep occurs after the age of 60 years.
NREM sleep has been thought to have several functions, such as energy conservation and growth. Growth hormone is produced in bursts during stages 3 and 4, and more cell division occurs during this type of sleep than during wakefulness. A controversial proposal has been that processing of information acquired during wakefulness occurs during NREM sleep.... sleep
People with sleep apnoea may not be aware of any problem during the night, but they may be sleepy during the day, with poor memory and concentration. Severe sleep apnoea is potentially serious and may lead to hypertension, heart failure, myocardial infarction, or stroke.
Obstructive sleep apnoea is the most common type and may affect anyone, but more often middle-aged men, especially those who are overweight. The most common cause is over-relaxation of the muscles of the soft palate in the pharynx, which obstructs the passage of air. Obstruction may also be caused by enlarged tonsils or adenoids. The obstruction causes snoring. If complete blockage occurs, breathing stops. This triggers the brain to restart breathing, and the person may gasp and wake briefly.
In central sleep apnoea, breathing stops because the chest and diaphragm muscles temporarily cease to work, probably due to a disturbance in the brain’s control of breathing. Causes include paralysis of the diaphragm and disorders of the brainstem. Snoring is not a main feature.People who are overweight may find losing weight helps.
Alcohol and sleeping drugs aggravate sleep apnoea.
In one treatment, air from a compressor is forced into the airway via a mask worn over the nose.
Night-time artificial ventilation may be needed.
Tonsillectomy, adenoidectomy, or surgery to shorten or stiffen the soft palate may be performed.... sleep apnoea
Physiological changes, such as a fall in temperature and blood pressure, take place just before sleep and continue during the early stages of NREM sleep. There is an intrinsic rhythm of sleep which in most subjects has a periodicity of around 25 hours. This can be modi?ed by external factors to bring it into line with the 24-hour day. Two peaks of a tendency to sleep have been identi?ed, and these usually occur between around 14.00–18.00 hours, and 02.00–06.00 hours. There are, however, di?erences according to age, in that, for instance, infants sleep for most of the 24 hours; during adolescence there is also an increase in the duration of sleep. Sleep requirements fall later in life, but there are wide genetic di?erences in the amount of sleep that people require and also the time at which they fall asleep most readily.
The internal clock can be disturbed by a variety of external factors which include irregular sleeping habits due, for instance, to shift work or jet lag. Sleep is also more likely to occur after physical exertion, reading and social activity. The duration and intensity of exposure to light can also modify sleep profoundly. Light promotes wakefulness and is the main factor that adjusts the 25-hour internal rhythm to the 24hour daily cycle. Neural connections from the retina of the EYE act on an area in the brain called the supra-chiasmatic nucleus which stimulates the pineal gland which produces MELATONIN. This is thought to trigger the range of neurological and metabolic processes that characterise sleep.... rapid-eye-movement (rem) sleep
Vigorous respiratory movements are made to overcome the obstruction during each apnoea. These are associated with snoring and snorting noises. The apnoea ends with a mini-arousal from sleep. As a result, sleep becomes fragmented and sleep deprivation, manifested as sleepiness during the day, is common. This may result in accidents – for instance, at work or while driving – and sleep apnoea is also linked with an increased risk of STROKE, heart attacks and HYPERTENSION.
The diagnosis of sleep apnoea has recently been facilitated by linking specially designed software with ELECTROCARDIOGRAPHY performed during sleep, with minimal disturbance of the subject.
Initial treatment is directed at correcting the cause (e.g. obesity), but if the apnoeas persist or are severe a nasal mask and pump which introduces air under slight pressure into the upper airway (continuous positive airway pressure, CPAP) is almost invariably e?ective.... sleep apnoeas
Irritability and a shortened attention span may occur after a short night’s sleep.
Longer periods without sleep leave a person increasingly unable to concentrate or perform normal tasks.
Three or more sleepless nights may lead to hallucinations and, in some cases, to paranoia.... sleep deprivation
They include benzodiazepines, antihistamines, antidepressants, and chloral hydrate.
Sleeping drugs may cause drowsiness and impaired concentration on waking.
Long-term use may induce tolerance and dependence.... sleeping drugs
Parasomnias These include medical disorders such as ASTHMA, ANGINA PECTORIS or EPILEPSY which are made worse by sleep, and a range of behavioural alterations which are usually related to a speci?c sleep stage or to a change from one state of sleep to another. Sleepwalking, night terrors, and nightmares are examples.
Insomnia Insomnia is de?ned as a di?culty in initiating or maintaining sleep. It affects around 15 per cent of the population at any one time, and is often due to a poor pre-sleep routine (e.g. taking excessive stimulants such as ca?eine); unsatisfactory sleep due to poor environments such as an uncomfortable bed or a cold or noisy bedroom; anxiety and/or depression; or occasionally to a physical problem – for example, pain – or a medical disorder associated with sleep such as obstructive SLEEP APNOEAS or periodic limb movements.
Excessive daytime sleepiness This is usually due to sleep deprivation caused either by inadequate duration of sleep, or by poor quality of sleep. The individual’s lifestyle is often a cause and modi?cation of this may relieve the problem. Other common causes of excessive daytime sleepiness are depression, obstructive sleep apnoeas, periodic limb movements, excessive alcohol or other drug intake, and, less commonly, NARCOLEPSY.... sleep, disorders of
Sleepwalking is usually calm and aimless, although it is sometimes more frantic when it occurs with night terror.
Some people regularly sleepwalk.
Sleepwalking in children is not normally a cause for concern and tends to disappear with age.
In adults, it may be related to anxiety or the use of sleeping drugs.... sleepwalking
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