Periodic limb movement disorder and restless legs syndrome in children with attention-deficit hyperactivity disorder

Sleep disruption can lead to symptoms of attention-deficit hyperactivity di sorder (ADHD) in children. Since periodic limb movement disorder and/or res tless legs syndrome can cause sleep disruption, we assessed whether these t wo specific sleep disorders are likely to occur in children with ADHD. We a sked a series of 69 consecutive parents of children with ADHD questions abo ut the symptoms of periodic limb movement disorder. Based on a positive res ponse to these periodic limb movement disorder queries, 27 children underwe nt all-night polysomnography. Eighteen children (aged 2 to 15 years) of the 27 (26% of the 69 children with ADHD) had 5 or more periodic leg movements in sleep per hour of sleep and had complaints of sleep disruption, thus fu lfilling the criteria for periodic limb movement disorder. A comparably age - and sex-matched group of children referred to a sleep laboratory for slee p complaints but without ADHD showed only a 5% prevalence (2 of 38 subjects ) of periodic leg movements in sleep (P=.017). Eight of the 18 children wit h ADHD and periodic limb movement disorder and one of the two control patie nts with periodic limb movement disorder had both a personal and parental h istory of restless legs syndrome symptomatology. This study further documen ts the occurrence of periodic limb movement disorder and restless legs synd rome in children and is the first large-scale study establishing a possible comorbidity between ADHD and periodic limb movement disorder. We propose t hat the sleep disruption associated with periodic limb movement disorder an d restless legs syndrome and the motor restlessness of restless legs syndro me while awake could contribute to the inattention and hyperactivity seen i n a subgroup of ADHD-diagnosed children.