Sleep disturbance is by far one of the most reported problems (>80%) especially by parents and care-takers, who commonly recount restless, inadequate and often delayed and/or fragmented sleep in their children.
A clear distinction, however, needs to be drawn between subjective and objective sleep reports and, with respect to the latter, actigraphyc versus video-polysomnographic (vPSG) studies present a palpable difference in terms of method and quality of data accessed. Several metanalytic reviews have been published within the last ten years, dealing with many confounding factors including gender, referral source, age range, co-morbid disorders, first versus follow-up visits, medications, number of studied nights with or without adaptation. (Owens, 2005; Cortese et al., 2006; Sadeh et al., 2006). They all address, through various approaches, the multilevel/dimensional relationship among sleep alterations and neurobehavioral/neurocognitive functioning.
In particular, the interaction of sleep with attention/ arousal mechanisms in children has been highlighted by most recent studies.
Items more often referred to by subjective studies on sleep and alertness in ADHD include (Cortese et al., 2006): bedtime resistance, sleep onset insomnia, night awakening, sleep duration, restless sleep, parasomnias, problems with morning awakening, sleep disordered breathing (SDB) excessive daytime sleepiness (EDS).
No major differences between adolescents with ADHD and controls were detected (Mick et al., 2000) after excluding confounding factors such as medications and psychiatric comorbidity. As for ADHD children, significantly over reported by comparison with controls were EDS (Marcotte et al., 1998, Owens et al., 2000), whether or not sleep disordered breathing (SDB) related, movements during sleep (Corkum et al., 1999, Owens et al., 2000). Also a longer sleep duration with increased night awakenings and parasomnias were observed upon comparison with controls (Owens et al., 2000). Despite the fact that bedtime resistance and sleep onset insomnia did not come across as significantly different by comparison with control subjects, after controlling for psychiatric co-morbidity and medications, it cannot be ruled out that a subgroup of ADHD children may display significant difficulties with sleep onset. Endogenous circadian alterations have been postulated by several authors (Vander Heijden et al., 2005) along with forced ultradian cycling (Kirov et al., 2004), which would make these children more prone to a delayed sleep phase (DSP). In this respect, melatonin use before bedtime with different regimen schedules and dosing has been acknowledged by several clinicians (Hodgkins et al., 2011; Owens et al., 2010; Larzelere et al., 2010).
Only a few actigraphic studies (Wiggs et al., 2005; Dagan et al., 1997; Corkum et al., 2001) and few video PSG studies were obtained in ADHD children, probably due to objective constraints as imposed by health policies, children restless and oppositional behavior and parents' reticence to over-night hospitalization. Concerning actigraphic studies, measures of objective sleep patterns (sleep duration, activity mean, wake time and number of awakenings) resulted not predictive of ADHD symptom severity after regression analysis (Wiggs et al., 2005) and did not correspond to parents' reports except for waking time in the morning. In particular, bedtime for the IADHD children was usually grossly underestimated by their parents, probably because of less externalizing behaviors during daytime.
Correspondence between subjective and objective assessment has been usually inconsistent with a few exceptions (Acebo et al., 1999). In fact, despite an overall very high parental report of sleep disturbance, actigraphic data did not confirm parents' concerns. Of course, some of these results could rely on the inherent incapacity of actigraphy to confirm specific sleep disorders such as SDB or sleep fragmentation at a microstructural level. Nevertheless, these results may still prove of some utility in order to provide parental reassurance and correct some of their distorted beliefs.
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