The prevalence of dyssomnias and parasomnias was determined in a longitudinal study of a sample of 2223 infants born in 1997-98 in the province of Quebec, Canada, and reported from the Sleep Disorders Center, Sacre-Coeur Hospital, University of Montreal. Self-administered questionnaires were completed by the mothers when the children reached 2.5 years of age, and at intervals up to 6 years. Dyssomnias manifested by frequent night wakings (-/>1 per night) and difficulty falling asleep at night (-/>30 min) were reported in 36.3% and 12.2% children at age 2.5 years, respectively. At age 6 years, the percentage with frequent night wakings had decreased steadily to 13.2%, and the percentage with difficulty falling asleep had decreased significantly to 7.4%. Between 2.5 and 6 years, the percentage with difficulty falling asleep had first increased to 16.0% at ages 3.5 and 4 and then decreased to 10% at age 5 and to 7.4% at age 6.
The overall prevalence of parasomnias from 2.5 to 6 years was as follows: somnambulism, 14.5%; sleep terrors, 39.8%; somniloquy (talking during sleep), 84.4%; enuresis, 25.0%; bruxism, 45.6%; and rhythmic movements, 9.2%. Sleep terrors were more frequent at ages 2.5, 3.5, and 4 than at ages 5 and 6. Rhythmic movements (body-rocking and head-banging) were more prevalent at age 2.5 than at all later ages. Boys outnumbered girls (ratio 2:1) with somnambulism and enuresis, but no gender differences were observed for prevalence of other parasomnias. Persistent somnambulism was correlated with persistent sleep terrors (P<.01) and persistent somniloquy (P<.001). Persistent sleep terrors were correlated with persistent somniloquy (P<.001), and with frequent night wakings (P<.001).
Children with persistent dyssomnias had higher separation anxiety scores, and had been put to bed already asleep in a greater proportion.at 2.5 years. Sleep-onset difficulties were associated with low socioeconomic status (SES), but not with co-sleeping or separation anxiety. Neither dyssomnia was associated with ADHD. Persistent parasomnias were associated with separation anxiety. They had little impact on sleep duration. Persistent somnambulism was related to a high ADHD score. Sleep terrors were related to a recent divorce of parents. Persistent rhythmic movements were related to insufficient SES and maternal depression. 
COMMENT. The prevalence of night wakings and sleep-onset problems is high in preschool children but symptoms lessen by 6 years of age. Parasomnias are also prevalent in early childhood and are associated with separation anxiety. Sleep terrors are associated with somnambulism, somniloquy, and frequent night wakings.
Night terrors and nocturnal frontal lobe epilepsy (NFLE). The differentiation of parasomnias and NFLE may be difficult, and the two diagnoses may co-exist. Night terrors in early childhood are sometimes followed by NFLE in school-age children. The Frontal Lobe Epilepsy and Parasomnias (FLEP) scale [2, 3] is considered reliable in distinguishing these disorders. A video-polysomnographic recording may be necessary to confirm the diagnosis in some cases.