J. Kaprio1,2, C. Hublin3, M. Partinen3, K.Heikkilä1, & M. Koskenvuo4
Parasomias are phenomena that intrude into, or occur during, sleep without becoming primary disorders of the states of sleep and wakefulness, per se. Although many are quite common and well-known to the general population, their epidemiology is poorly understood, and no large, representative twin studies have been carried out. For these reasons, we investigated genetic and environmental effects on sleeptalking, nocturnal enuresis, and nightmares. Similar analyses of sleepwalking and bruxism have been published (C. Hublin, et al, 1997, Neurology, 48,177-181, J. Sleep Res., in press). Methods: A questionnaire sent, in 1990, to Finnish Twin Cohort subjects aged 33-60 years, yielded responses from 11,220 twins with complete data for all items on occurrence of common parasomnias during childhood, and as adults. Included were responses from both members of 1,298 MZ and 2,149 like-sex DZ twin pairs. Mx models were fit to these data, in most models, separately by gender. Results: Genetic factors accounted for 67-70% of the phenotypic variance in childhood enuresis; too few subjects reported enuresis in adulthood to permit analyses. For nightmares, additive genetic factors accounted for 44-45% of phenotypic variance in childhood and for 36-38% of variance in nightmare reports by adults. Finally, genetic factors accounted for 51-54% of the variance in sleeptalking in childhood and 37-48% in adulthood. The genetic correlation between childhood and adult sleeptalking was high, but only adult sleeptalking was associated with increased risk of serious psychopathology, assessed using medical register data. Summary: Sleeptalking, nightmares, and nocturnal enuresis in childhood are common parasomnias with modest to strong genetic components.
Address: Department of Public Health, P.O. Box 41, Mannerheimintie 172, FIN-00014, Helsinki, Finland, 358-9-19127595 (ph), 358-9-19127600 (fax), jaakko.kaprio@helsinki.fi
1Department of Public Health, University of Helsinki, Helsinki, Finland 2Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki 3Haaga Neurological Research Centre, Helsinki 4Department of Public Health, University of Turku, Turku, Finland