Epidemiology
In general, non-rapid eye movement (NREM) parasomnias are more prevalent in children and occur in people less than 50 years old.[1]
NREM sleep parasomnias
Confusional arousals have a lifetime prevalence reported as 18.5% and among adults over 15 years prevalence is 2.9% to 4.2%.[2]
Sleepwalking is a common parasomnia in childhood, occurring in up to 2% of the population.[3] In adults, the prevalence is about 1% to 4%.[4][5] Most children outgrow the parasomnia in their mid-teens. Sex does not appear to play a role in European studies, and this is also believed to hold true for the US population.[6]
Sleep terrors affect approximately 6.5% of children.[5] Prevalence in adults has been reported at 2.3% to 2.6% in people aged 15-64 years, and 1% in people aged 65 years and older.[2] Among children, sleep terrors are more common in boys than in girls but no sex difference is reported in adults.[1]
Sleep-related eating disorder has been recorded in 5% of a sample 700 people, including outpatients and inpatients with an eating disorder, obese people in a trial for an anorexic agent, depressed patients in an antidepressant trial, and a group of unselected college students.[7] Randomly picked controls (who did not have an eating disorder history, were not part of the cohort in a trial for an anorexic agent, and were not depressed patients taking an antidepressant) formed the unselected college student group in the trial. The highest prevalence was noted in the inpatient eating disorders group (16.7%), followed by the outpatient eating disorders group (8.7%); 4.6% of the unselected student population also reported the problem.[7]
Rapid eye movement (REM) parasomnias
Rapid eye movement sleep behaviour disorder (RBD) is a type of REM parasomnia. It has an estimated prevalence of 0.68% (0.29% to 1.15%) when confirmed by polysomnography (PSG). The prevalence of probable RBD (by history and not PSG-confirmed) is higher at 4% to 6%, but the higher estimate may be due to false positives.[8] Exact incidence is unknown. This parasomnia typically affects older men, but when it occurs in younger people, men and women are equally affected.[2]
Recurrent isolated sleep paralysis prevalence rates have been noted to differ across nationalities in comparative studies.[2] One study reported a prevalence of 11.4% in American students, compared with 19.2% and 20.7% in students from Kuwait and Sudan, respectively.[9] Cultural differences may explain some of the variability in prevalence. In Asian cultures, the 'ghost oppression' phenomenon (kanashibari) corresponds to the symptoms recognised in the western hemisphere as sleep paralysis. More accurate prevalence estimates can be obtained by accounting for such differences when study questionnaires are prepared.[10] Although often reported by younger subjects, isolated sleep paralysis may be under-recognised in older people. A prevalence of almost 18% for isolated sleep paralysis symptoms has been reported in a cohort of Chinese patients >70 years of age.[11] One study documented the overall prevalence to be between 2.3% and 40% and reported a 2 to 1 female to male ratio.[12]
Nightmare disorder is more prevalent in children. It also occurs more frequently in women than in men, with an overall prevalence of 5% to 8% in adults.[13][14]
Other parasomnias
Exploding head syndrome has been reported at all ages, but seems to be particularly prevalent in younger adults; occurring in about 16.6% of college students. It is more common among those who also experience sleep paralysis. Overall prevalence in the general population and global trends in epidemiology are unknown. Whether or not it is more common in women remains controversial.[15]
Sleep-related hallucinations prevalence estimates are available from studies in non-institutionalised European people, and prevalence in the US is likely to be similar. A large cohort of >15,000 people in the UK, Germany, and Italy, aged ≥15 years, reported hallucinations at sleep onset (24.8%) and on awakening (6.6%). Younger patients are more likely to be affected, and women may be slightly more at risk. There are no known global trends in epidemiology.[16]
The prevalence of enuresis varies widely with age, from 2% in older adults to 30% in school-age children.[17]
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