OBJECTIVE. There is growing evidence that genetic factors are involved in the occurrence of sleep terrors. Twin studies provide invaluable information regarding genetic and environmental factors that can affect the manifestation of the disease; however, most previous twin studies on sleep terrors were performed retrospectively or with a sample that was too small to yield conclusive results. The aim of this large prospective study was to clarify the genetic and environmental contributions to sleep terrors in childhood. METHODS. In all, 390 pairs of monozygotic and dizygotic twins were recruited at birth for a longitudinal study. The prevalence and frequency of sleep terrors were assessed at 18 and 30 months of age with a questionnaire administered to the biological mother of the twins. Zygosity was determined by a questionnaire and genotyping. The prevalence and polychoric correlation for each type of twins were calculated. Structural-equation modeling was used to determine the proportion of variance attributable to additive genetic, shared, and nonshared environmental factors. RESULTS. The prevalence of sleep terrors was 36.9% at 18 months and 19.7% at 30 months; 49% of affected children were boys, and 51% were girls. At 18 months, the polychoric correlations were 0.63 for monozygotic and 0.36 for the dizygotic twins. These were 0.68 (monozygotic) and 0.24 (dizygotic) at 30 months. Our model-fitting analysis showed that sleep terrors were explained by a 2-component model at 18 months (43.7% additive genetic effects and 56.3% nonshared environment) and at 30 months (41.5% additive genetic effects and 58.5% nonshared environment). CONCLUSIONS. These results strongly support the heritability of sleep terrors. There also seems to be continuity in genetic effects with the persistence of sleep-terror symptoms.
OBJECTIVES. Our aim for this study was to determine the prevalence of dyssomnias and various parasomnias in early childhood and to describe their temporal evolution, gender differences, and correlates. METHODS. This research is part of a longitudinal study of child development. A randomized, 3-level, stratified survey design was used to study a representative sample of infants who were born in 1997–1998 in the province of Quebec (Canada). When the children were 2.5 years of age, 1997 families agreed to be interviewed. The presence of dyssomnias or parasomnias was obtained from a self-administered questionnaire that was completed by the mother at each round of measures. RESULTS. The percentage of children with frequent night wakings decreased steadily from 36.3% at age 2.5 to 13.2% at age 6. Similarly, the percentage of children who had difficulty falling asleep at night decreased significantly from 16.0% at ages 3.5 and 4 to 10% at age 5 and to 7.4% at age 6. The overall prevalence of each parasomnia for the period studied was as follows: somnambulism, 14.5%; sleep terrors, 39.8%; somniloquy, 84.4%; enuresis, 25.0%; bruxism, 45.6%; and rhythmic movements, 9.2%. Persistent somnambulism at age 6 was significantly correlated with sleep terrors and somniloquy. Persistent sleep terrors at age 6 were also correlated with somniloquy. Finally, persistent sleep terrors at age 6 were correlated with frequent night wakings. Separation anxiety was associated with persistent night wakings and with somnambulism, bruxism, sleep terrors, and somniloquy. CONCLUSIONS. There is a high prevalence of night wakings and sleep-onset difficulties in preschool children. Parasomnias are highly prevalent in early childhood and are associated with separation anxiety. However, they have little impact on sleep duration.
Objectives. This study examines the prevalence and developmental changes of parasomnias and assesses gender differences, relationships between parasomnias, and associations with anxiety and family adversity using data collected during the course of a longitudinal study of a representative sample of children from Québec. Method. The present analyses are based on results available for 664 boys and 689 girls for whom mothers have completed questions concerning demographics, parasomnias, and anxiety level. For the prevalence and developmental aspects of parasomnias, prospective data were collected at annual intervals from 11 to 13 years old and retrospective data for the period between ages 3 and 10 years were collected when the children were 10 years old. Results. Somniloquy, leg restlessness, and sleep bruxism are the most frequent parasomnias. More girls were afflicted with leg restlessness, while enuresis and somniloquy were more common in boys. High anxiety scores were found in children suffering from night terrors, somniloquy, leg restlessness, sleep bruxism, and body rocking. Parasomnias were unrelated to the index of family adversity. Conclusions. Although sleepwalking, night terrors, enuresis, and body rocking dramatically decreased during childhood, somniloquy, leg restlessness, and sleep bruxism were still highly prevalent at age 13 years, paralleling results found in adults. Sleepwalking, night terrors, and somniloquy are conditions often found together. The only robust gender difference was for enuresis. High anxiety scores in parasomnias are reported for the first time in a large, controlled study. Sociodemographic variables do not seem to play a major role in the occurrence of parasomnias.