Original ArticleA prospective study of sleep problems in children with ADHD
Introduction
Attention-deficit/hyperactivity disorder (ADHD) affects 5% of children worldwide [1], and these children are two to three times more likely to experience sleep problems compared with their typically developing peers [2], [3]. Children with ADHD commonly experience sleep problems such as sleep-onset delay, bedtime resistance, and night awakenings [4], [5]. These problems are usually behavioral in nature (i.e., thought to originate from a non-biological cause) but can also be the result of undiagnosed biological sleep problems (e.g., restless legs syndrome or sleep disordered breathing) [6], which are also more common in children with ADHD, compared with typically developing children [7], [8]. Sleep problems in children with ADHD are associated with poorer daily functioning [5] and while they have long been recognized in this group [9], [10], their persistence or otherwise remains largely unknown. Longitudinal data are required to establish sleep problem trajectories in children with ADHD, which can inform clinicians about their prognosis. Identifying which child/family factors and types of sleep problems put children at risk of persistent sleep problems would also allow for better targeting of early intervention and prevention efforts.
In typically developing children, sleep problems have been shown to be largely transient. A population-based study of children (n = 4460) showed that 13% of children aged 4–5 years had moderate/severe sleep problems by parent report, yet two years later sleep problems persisted in only 3% [11]. This picture appears more complicated for children with mental health difficulties [12] and neurobehavioral disorders such as ADHD [3]. The strong neurological overlap between the structures involved in ADHD and sleep are likely to play a contributing role to elevated sleep problems in this group [3], [13]. However, only two longitudinal studies to date have examined sleep problems in children with ADHD. In a clinical sample (7–13 years, n = 76), 72% of sleep problems persisted from baseline to 18 months in children with ADHD and/or anxiety. Child age and gender, parent education level, and total number of stressful life events did not predict sleep problems 18 months on but sleep problems at baseline did [14]. These findings are limited in how they generalize to children with ADHD managed by clinicians because of the inclusion of children with anxiety only and exclusion of children taking ADHD medication [15]. Children with ADHD have also been shown to have shorter sleep duration than children without ADHD by parent report from birth to 11 years, and this was statistically significant at ages 5.9, 6.9, and 9.7 years [16]. Yet, this study did not examine the persistence of sleep problems per se over time.
Cross-sectionally, sleep problems in children with ADHD have been associated with greater ADHD symptom severity [5], [17], [18]; ADHD medication [19], [20], [21]; internalizing [17], [22], [23] and externalizing comorbidities [18], [23], in particular when they co-occur [24]; and poorer parental mental health [5]. Yet, the cross-sectional nature of these studies makes it impossible to delineate whether these factors are predictors or consequences of sleep problems. Thus, longitudinal data are required to identify risk factors for sleep problem trajectories.
We therefore aimed, in a large, multisite sample of children with ADHD, to examine:
- 1
behavioral sleep problem trajectories over a 12-month period,
- 2
types of sleep problems experienced, and
- 3
risk and protective factors for sleep problem trajectories.
Section snippets
Design and setting
This longitudinal study draws on data collected across three time points – baseline, 6, and 12 months – from two harmonized studies. All participants were recruited from the same sampling frame – 21 public and private pediatric practices across Victoria, Australia. Children with moderate/severe behavioral sleep problems at baseline were enrolled in a randomized control trial (RCT) [25] of a behavioral sleep intervention, while those with no/mild sleep problems were enrolled in a cohort study
Recruitment and follow-up
We assessed 827 children for eligibility, of whom 561 were eligible and 392 (70%) enrolled (see Fig. 1). Enrolled children were comparable to those who chose not to participate based on child age, gender, and family socioeconomic status.
Of the 392 enrolled children, (148 with no/mild (cohort study) and 244 with moderate/severe sleep problems (RCT)), 122 were excluded as they were allocated to the intervention arm of the RCT, which left 270 children for this longitudinal study. Sleep problem
Discussion
This is the first large, prospective cohort study to examine sleep problem trajectories and their risk factors in children with ADHD. While the majority of sleep problems were transient over a 1-year period, they persisted in 1 in 10 children. A diversity of sleep problems was experienced by children in both the transient and persistent trajectories. Risk factors for persistent sleep problems include co-occurring internalizing and externalizing comorbidities, ADHD medication use and greater
Conclusion
Sleep problems are usually transient in children with ADHD; however, in a subgroup of children, they tend to persist in the medium term. These findings flag children at risk and inform sleep problem trajectories in children with ADHD. Clinically, we recommend tracking sleep problems over time in children with ADHD with the brief screening question. Treating co-occurring internalizing and externalizing comorbidities may also hold promise for reducing sleep problems in children with ADHD and vice
Financial disclosure statement for all authors
This project is funded by a Project Grant from the Australian National Health and Medical Research Council (NHRMC) (607362) and Community Child Health at the Murdoch Childrens Research Institute (MCRI). Dr Sciberras and Dr Mensah are funded by NHMRC Early Career Fellowships in Population Health (1037159 and 1037449). Ms Lycett is funded by an MCRI Postgraduate Health Scholarship. A/Prof. Hiscock's position is funded by an NHMRC Career Development Award (607351). MCRI is supported by the
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2014.06.004.
Acknowledgments
We thank all families and pediatricians for taking part in the study. We also thank the Sleeping Sound with ADHD and Attention to Sleep research teams for their contributions to the study.
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