Original ArticlePrevalence of different parasomnias in the general population
Introduction
Parasomnias are undesirable physical events or experiences that occur during entry into sleep, within sleep, or during arousals from sleep [1]. The events are manifestations of central nervous system activation. They are divided into disorders of arousal (from non-rapid eye movement [NREM] sleep), parasomnias associated with rapid eye movement (REM) sleep, and other parasomnias. All parasomnias can be diagnosed based on subjective reports from the patient, parent or caregiver, except for REM sleep behaviour disorder where the diagnosis requires polysomnographic documentation [1].
The disorders of arousal (sleep walking, confusional arousal, and sleep terror) are commonly seen in children, but adults may also experience such parasomnias [1], [2], [3]. Although not included as separate entities in the International Classification of Sleep Disorders (ICSD-2), sleep talking, sleep related violence, and sexual behavior during sleep are considered to belong to this group, as these phenomena often are present together with the disorders of arousal [1], [4], [5], [6]. All these parasomnias occur most commonly in the early part of the sleep period and usually in connection with slow wave sleep. Individuals are usually amnesic or partially amnesic for the event the next day.
Nightmare disorder, REM sleep behavior disorder (RBD), and recurrent isolated sleep paralysis are included in the group of parasomnias associated with REM sleep [1]. These parasomnias usually occur during the latter part of the sleep period, where REM sleep dominates. It is common to remember the event the next day, in contrast to the amnesia following NREM parasomnias.
Several parasomnias are not associated with specific sleep stages and thereby considered in the group of other parasomnias. Examples of these are sleep related groaning, sleep-related eating disorder, exploding head syndrome, sleep related hallucinations, and sleep enuresis [1].
It is not uncommon for an individual to have more than one parasomnia [1], [7]. Sometimes it is difficult to distinguish between different parasomnias, i.e., confusional arousal and sleep terror. The disorders of arousal can be considered on a continuum [3], with confusional arousal on one end and sleep terror and agitated sleep related violence on the other. The “parasomnia overlap disorder” is used as a diagnostic entity when RBD is observed in association with NREM parasomnias [1]. Several parasomnias can emerge in close association with specific sleep disorders, especially obstructive sleep apnea [1], [8]. Furthermore, parasomnias have been found to be associated with mental disorders, especially in adults [2], [9].
The prevalence of many of the parasomnias is unclear since there are few population based epidemiological studies. Several authors report that different wordings of a question about parasomnia may lead to very different estimates [10], [11]. Interestingly, Nielsen recently reported that a nonspecific question about dream enacting behavior gave a prevalence of 35.9%, whereas more elaborate questions produced higher prevalence, ranging from 77% to 98% [11]. Nielsen et al. conclude that retrospective, simple questionnaires may nonetheless prove valuable as screening tools for parasomnias.
Our aims of the present study were to explore the frequency of parasomnias in the general population through a telephone interview with relatively nonspecific single questions and to study the associations with gender, depressive mood, symptoms of sleep apnea, insomnia and restless legs. Furthermore, we wanted to study how many parasomnias each individual reported and the interrelationship between the different parasomnias.
Section snippets
Procedure
Data were collected by a telephone interview conducted by an opinion-research institute (Norsk Respons), employing the next birthday technique. In the next birthday technique the interviewer asks to speak to the adult member of the household who has the next birthday. This technique constitutes a procedure of randomly selecting individuals within a household preventing potential selection bias [12]. The sample was drawn randomly from a survey population, consisting of Norway’s register of phone
Results
Lifetime prevalence of the different parasomnias varied from about 4% to 67% (Table 2). Current prevalence was naturally lower, but still all parasomnias were reported at least once during the last 3 months (Table 2). Current prevalence and occurrence at least once a week varied from 0.0% (injured somebody else during sleep) to 6.0% (sleep talking) (Table 2).
Males reported more often having “injured yourself during sleep” compared to females (5.7% versus 2.9%, p = 0.031). Females reported more
Discussion
This is one of few population based studies investigating the prevalence of different parasomnias. The data suggest that several parasomnias, such as sleep walking, sleep talking, and nightmare, are highly prevalent in the general population. Not surprisingly, some respondents reported having several parasomnias [1], [7]. The prevalence for most parasomnias was comparable to other studies [1], [2], [11], [15]. However, the prevalence of injuring oneself (4.3%) or somebody else (3.8%) during
Conflict of interest statement
All authors declare that they have no conflicts of interest relevant to the subject of the paper.
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