Sleep disorders in psychiatric diseases. Epidemiological aspects
Dealberto, M.J.
L'Encephale 18(4): 331-340
1992
ISSN/ISBN: 0013-7006 PMID: 1297583 Document Number: 4606
Very few epidemiological surveys have specifically studied relationships between sleep disturbances and psychiatric diseases. In this review, we preferred to use the classification proposed in 1979 by the Association of Sleep Disorders Centers. It includes four main categories : insomnias, excessive sleepiness, troubles of the wake/sleep schedule and parasomnias. Evaluating psychiatric disorders among general populations is easier owing to DSM III and DSM III-R criteria, but there are not equivalent criteria in evaluating sleep disorders. It is almost impossible to realize polysomnographic recordings in large samples, therefore sleep disorders are to be detected by questionnaires. It has been shown that there is a good correlation between self-reports and polysomnographic recordings among clinical and general samples. The prevalence of insomnia, defined as difficulties of initiating and maintaining sleep, is estimated between 9 and 31 %. It is higher among women, elderly people, separated and divorced subjects, and low educational levels' groups. It has to be noticed that polysomnographic records of some subjective insomniacs are not different from those of good sleepers, sleep latency excepted. These subjective (and not objective) insomniacs have high scores in anxiety scale, depression scale, or psychologic distress. Insomnia is more frequently noted amongst subjects with psychiatric diagnoses, especially major depressive disorders and anxiety disorders. Depressive disorders are present in 2140 % of insomniacs versus 0-1 % of non-insomniacs, and anxiety disorders in 13-24 % of insomniacs versus 3-10 % of non-insomniacs. In depressive disorders, sleep alterations are frequently noted: they are difficulties of initiating and maintaining sleep, decreasing proportion of slow-wave sleep, decreasing time of REM (rapid eye movement) sleep and REM sleep latency, and increasing density of REM sleep. Of these modifications, the last two ones seem to be specific for depression. The relationships between sleep, aging and depression are more complex than previously noted. For example, differences between depressed and non-depressed subjects depend on the age of the population. The prevalence of hypersomnia is lower than the insomnia's. It varies between 2 and 4 %. It is more frequently noted among young people, and never married subjects. Two specific aetiologies must be looked for: sleep apnea syndrome and narcolepsy. These diagnoses are respectively found in 45 % and 24 % of hypersomniacs examined in American Sleep Centers. Hypersomnias are objectived by the Multiple Sleep Latency Test, which measures the physiologic sleep tendency. As for insomnia, a strong relationship was noted between hypersomnia and psychiatric disorders, especially for depressive disorders (28 % of hypersomniacs versus 10 % of non-hypersomniacs) and anxiety disorders (10 % of hypersomniacs versus 1 % of non-hypersomniacs). There are sleep alterations in normal aging, mainly difficulties for maintaining sleep and decrease of sleep's depth. Alterations of the sleep/wake schedule are frequently found amongst demented subjects. Sleep electroencephalograms are abnormal in 90 % of Alzheimer's disease cases, versus 30 % of normal subjects of the same age. In Alzheimer's disease, there is an increase of number and duration of nocturnal awakenings, and a decrease of stade 3 and 4 of slow-wave sleep. But these alterations cannot be presented as markers for the early stades of the disease. Sleep apnea syndrome can allow either hypersomnia, or insomnie. The prevalence of sleep apnea syndrome is estimated between 1 and 5 %, and increases with age, reaching between 15 and 43 % among elderly subjects. Some clinical studies found an association between sleep apnea syndrome and varied psychiatric disorders: cognitive impairment, psychologic disorders, depressive symptoms. In conclusion, we need more accurate descriptive crosssectional studies to investigate the relationships between sleep disorders and psychiatric diseases according to age, sex, and sociocultural characteristics before undertaking longitudinal surveys with aetiologic design.
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