Periodic limb movements in sleep may predispose to attention deficit hyperactivity disorder if not the reverse
Year: 2023
Type: editorial
Abstract: We read with interest the article by Fulda and Miano “Time to rest a hypothesis? Accumulating evidence that Periodic Leg Movements during sleep are not increased in children with Attention Deficit Hyperactivity Disorder (ADHD): results of a case-control study and a meta-analysis” SLEEP 2023 In Press [1]. The authors conclude that ADHD does not predispose to Periodic Limb Movements in Sleep (PLMS) but there is a reverse hypothesis that has been little explored in the literature, namely that PLMS cause, predisposes to, or exacerbates ADHD. Although the data are largely preliminary, we and others have shown that this could be true and demonstrate that ADHD occurs very commonly in patients with PLMS at rates of 90.6% and 44.4%, respectively [2, 3]. There are good hypothetical reasons why this might be the case, the first and foremost being that the electroencephalography (EEG) arousals and the autonomic arousals with increases in blood pressure and heart rate that we and others have shown are associated with PLMS may, in turn, predispose to ADHD [4, 5]. The hypothesis is also supported by additional literature that shows increased numbers of autonomic arousals in ADHD children in the nighttime [6]. However, autonomic arousals were not recorded in the original aforementioned studies looking at the prevalence of ADHD in patients with PLMS [2, 3]. In addition, both studies were undoubtedly predisposed to referral bias since the populations studied were largely drawn from hospital populations where the prevalence of ADHD is likely to be high [2, 3]. This was partially ameliorated in the second of these studies where 520 children were drawn from the hospital population and 351 from a community sample [3]. Furthermore, neither study had any assessment of ADHD severity. Another issue is that, in these older studies, a more accurate way of discriminating PLMS such as the periodicity index was not yet available [7]. Neither study employed a true control group [2, 3]. In order to more fully explore whether PLMS predisposes to ADHD, an ADHD questionnaire and quantitative ADHD rating scale should be administered in the sleep laboratory to a convenience sample of children who do and who do not have PLMS so that a control group is present. Or better yet, if funding is available, a community sample can be chosen. EEG and autonomic arousals should be recorded and quantitated from all participants and correlations done thereafter. Iron may provide another link between PLMS and ADHD as both conditions are characterized by iron deficiency and both disorders are improved with iron therapy [8–13]. Ferritin and other iron parameters should be added to the study. One caveat is that the sample should not be chosen from centers that specialize in ADHD and patients referred to the center for evaluation of ADHD should be excluded in order to eliminate referral bias. Another caveat is that PLMS should be measured by employing more recent and more accurate techniques such as the periodicity index [7]. Patients with confounding disorders frequently associated with PLMS such as Restless Legs Syndrome, Narcolepsy, or rapid eye movement Sleep Behavior Disorder could be excluded from the study. One could also eliminate children from the analysis who have obstructive sleep apnea because of the well-known connection between ADHD and sleep apnea [14]. However, including children with sleep apnea in the analysis may also be informative. In such a study, Chervin et al., for example, suggested, based on their data, that Obstructive Sleep Apnea was a modifying factor between the more direct connection between PLMS as a causal effect of ADHD [14]. Another approach which we have employed in our previous research is to do a retrospective epidemiology study but to do it prospectively. In other words, all data are collected retrospectively but participants are followed forward in time to determine the outcome of interest. For example, in one of our previous studies, We looked at data in 2021 collected in the past from 2006 to 2014 [15]. Assuming records and an accurate database are available as in our previous study, one could follow patients with and without PLMS forward in time to see which patients did and did not develop ADHD. A cross-sectional epidemiology study would be an inferior design as it would not imply causality. None declared.
Source: SLEEP
Author: Arthur S Walters
Institution: Vanderbilt University
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W4327574695