NREM sleep instability is reduced in children with attention-deficit/hyperactivity disorder

STUDY OBJECTIVES: To evaluate non-rapid eye movement sleep instability (NREM), as measured by the cyclic alternating pattern (CAP), in a cohort of children with attention-deficit/hyperactivity disorder (ADHD) and normal controls. DESIGN: Prospective study. SETTINGS: Sleep laboratory. PARTICIPANTS: Twenty consecutive outpatients with ADHD (18 boys and 2 girls; age range 6-13 years, mean age 9.3 years) and 20 normal children matched for age and socioeconomic status underwent polysomnographic recordings for 2 consecutive nights in a standard laboratory setting. Sleep was visually scored for sleep macrostructure and CAP, according to standard criteria. MEASUREMENTS AND RESULTS: Children with ADHD showed significantly reduced sleep duration and increased rate of stage shifts. All children with ADHD had an apnea-hypopnea index less than 1. Those with ADHD presented lower total CAP rates and lower CAP rates during sleep stage 2 than did normal controls. Moreover, in children with ADHD, we found a lower number of CAP sequences and a reduced total A1 index, mainly in light sleep (sleep stages 1 and 2). We did not find differences in A subtype percentages, but there was a longer duration of A1 subtypes in children with ADHD. CONCLUSIONS: Children with ADHD showed a lower CAP rate and a lower number of CAP sequences; this supports the hypothesis of the existence of a hypoarousal state in these patients.