To evaluate the association of short sleep duration with behavioral symptoms of ADHD, a cross-sectional study of children born in 1998 in Helsinki, Finland, was conducted by researchers at the Universities of Helsinki and Oulu, Finland. Sleep quality was measured using actigraphs, and the Sleep Disturbance Scale for Children and the ADHD Rating Scale IV were administered to parents. Of 280 children (134 boys, 146 girls) with a mean age of 8.1 years (range 7.4-8.8), those with a short average sleep duration (<7.7 hours) had higher hyperactivity/impulsivity and ADHD total scores, but similar inattention scores compared with children sleeping 7.7 to 9.4 hours or >9.4 hours. Short sleep duration remained significantly associated with hyperactivity/impulsivity when controlling for basic confounding variables and also for sleeping difficulties and somatic illnesses, but it was not related to inattention or the ADHD total score. Short sleep duration was not correlated with sleeping difficulties, but sleep-breathing disorder was significantly associated with hyperactivity/impulsivity, inattention, and ADHD total score. Parent-reported short sleep duration was not related to hyperactivity/impulsivity, inattention, and the ADHD total score. 
COMMENT. Short sleep duration measured objectively with the actigraph and parent-reported sleeping difficulties are independently associated with increased risk of behavioral symptoms of ADHD. One third of children in the US are estimated to have inadequate sleep . Questions regarding sleeping habits are important in the evaluation of children with ADHD, especially in relation to the symptoms hyperactivity/impulsivity and their association with short sleep duration or sleeping difficulties, such as sleep-breathing disorder and snoring. Short sleep duration is not correlated with the symptoms of inattention. A causal relation between sleep duration and behavioral symptoms is not established, but maintaining regular sleeping schedules may help to ameliorate the hyperactivity and impulsivity of ADHD. Sleep duration and sleeping difficulty studies are often inaccurate, relying heavily on parental reports, which are susceptible to bias. In a child with hyperactive behavior, excessive snoring should prompt referral to ENT, and sleeping difficulties may indicate the need for a polysomnograph. However, polysomnographic sleep scores are not related to academic functioning, IQ and neuropsychological test cores are powerful predictors of achievement. (Mayes SD et al. 2008). Inattentive symptoms are sometimes related to daytime sleepiness. (Willoughby MT et al. 2008).
Girls with ADHD generally have a greater frequency of the inattentive subtype than boys, but overall, boys outnumber girls with a 4:1 ratio for the ADHD-HI and 2:1 for ADHD-AD. (Wolraich ML et al. 1996). The preponderance of girls in the above study is unusual, but apparently, gender was not a modifying factor.