Abstract
Recently, measuring the complexity of body movements during sleep has been proven as an objective biomarker of various psychiatric disorders. Although sleep problems are common in children with autism spectrum disorder (ASD) and might exacerbate ASD symptoms, their objectivity as a biomarker remains to be established. Therefore, details of body movement complexity during sleep as estimated by actigraphy were investigated in typically developing (TD) children and in children with ASD. Several complexity analyses were applied to raw and thresholded data of actigraphy from 17 TD children and 17 children with ASD. Determinism, irregularity and unpredictability, and long-range temporal correlation were examined respectively using the false nearest neighbor (FNN) algorithm, information-theoretic analyses, and detrended fluctuation analysis (DFA). Although the FNN algorithm did not reveal determinism in body movements, surrogate analyses identified the influence of nonlinear processes on the irregularity and long-range temporal correlation of body movements. Additionally, the irregularity and unpredictability of body movements measured by expanded sample entropy were significantly lower in ASD than in TD children up to two hours after sleep onset and at approximately six hours after sleep onset. This difference was found especially for the high-irregularity period. Through this study, we characterized details of the complexity of body movements during sleep and demonstrated the group difference of body movement complexity across TD children and children with ASD. Complexity analyses of body movements during sleep have provided valuable insights into sleep profiles. Body movement complexity might be useful as a biomarker for ASD.
Highlights
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by difficulties with social interaction and communication [1]
Results showed that all 34 subjects × 3 times of the raw data and 92.2% of the thresholded data were rejected for stationarity at the 0.05 level of significance
These results indicate that the distributions of both the magnitude and the presence of body movements are significantly different between the first and latter half of sleep, i.e., the magnitude and the presence of body movements were non-stationary overnight
Summary
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by difficulties with social interaction and communication [1]. Many results of earlier studies have demonstrated that children with ASD commonly experience sleep problems [2,3,4], and that they are more likely to persist than in typically developing (TD) children [5,6,7,8,9]. Good agreement between actigraphy and PSG has been reported from sleep assessments of children with ASD [25]. Across individuals, children with ASD experience different sleep difficulties such as insomnia, circadian rhythm disorder, and parasomnia. Such difficulties might be attributable to various factors such as circadian-relevant gene anomalies, abnormal melatonin rhythms, brain wave organization, hyper-arousal, sensory hyper-reactivity, and various stresses, suggesting great heterogeneity of sleep problems in children with ASD [3,16]. Some earlier studies have shown significant alterations of movement complexity in patients with bipolar disorder [29,30,31,32,33], dementia [34,35], and insomnia [36]
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