<p><strong>CONTEXT: </strong>Sleep is critical for optimal childhood metabolic health and neurodevelopment. However, there is limited knowledge regarding childhood sex differences in sleep, including children with neurodevelopmental disorders, and the impact of such differences on metabolic health.</p>

<p><strong>OBJECTIVE: </strong>To evaluate if sex differences in childhood sleep exist and if sleep associates with metabolic health outcomes equally by sex. Using autism spectrum disorder (ASD) as a case study, we also examine sleep sex differences in children with a neurodevelopmental disorder.</p>

<p><strong>METHODS: </strong>A narrative review explored the literature focussing on sex differences in childhood sleep.</p>

<p><strong>RESULTS: </strong>Sex differences in sleep were not detected among pre-adolescents. However, female adolescents were more likely to report impaired sleep than males. Childhood obesity is more common in males. Shorter sleep duration may be associated with obesity in male pre-adolescents/adolescents; although findings are mixed. ASD is male-predominant; yet, there was an indication that pre-adolescent female children with ASD had more impaired sleep.</p>

<p><strong>CONCLUSION: </strong>Sex differences in sleep appear to emerge in adolescence with more impaired sleep in females. This trend was also observed among pre-adolescent female children with ASD. Further research is needed on sex differences in childhood sleep and metabolic health and the underlying mechanisms driving these differences.</p>

<p><strong>LAY ABSTRACT: </strong>Higher levels of physical activity may be associated with improved sleep in children, but this relationship is still being determined, especially in autistic children. In this study, we used existing data from the 2018 National Survey of Children's Health. Caregivers of children 6-17 years old, including caregivers of autistic children, completed a questionnaire that included questions about physical activity (days active in the past week) and sleep duration. We then determined if children were obtaining the recommended hours of sleep for their age (i.e. sufficient sleep). We found that higher physical activity levels were associated with sufficient sleep duration, but this finding was weaker in autistic children. In particular, this association was not observed in autistic children with more severe autism spectrum disorder, female autistic children, and autistic children 6-12 years old. In conclusion, physical activity is a promising approach to help children obtain sufficient sleep duration. However, more personalized approaches to improving sleep may be needed for certain groups of autistic children.</p>

<p>Autistic children and adults often have sleep disturbances, which may affect their and their family's quality of life. Yet, the relationship between sleep-wake patterns and autism spectrum traits is understudied. Identifying such relationships could lead to future research elucidating common mechanistic underpinnings. Thus, we aimed to determine whether sleep-wake patterns, specifically related to sleep, physical activity, and the daily sleep-wake rhythm (i.e., circadian rhythm), are associated with autism spectrum-related traits. Accelerometer-derived sleep-wake parameters were estimated in individuals with autistic spectrum traits and their family members (N&nbsp;=&nbsp;267). We evaluated autism spectrum traits using the Social Responsiveness Scale (SRS) to assess the presence and severity of social impairment and the Behavior Rating Inventory of Executive Function (BRIEF) to assess executive function. The linear multivariate regression analysis (using SOLAR-Eclipse) showed that in adults, increased core autism spectrum traits and executive dysfunction were associated with disruption of several sleep-wake parameters, particularly related to the daily sleep-wake rhythm, and that executive dysfunction was associated with disrupted sleep quality and level of physical activity. We highlight the interplay between daytime function and disrupted sleep-wake patterns, specifically related to the daily sleep-wake rhythm, that could guide future research into common mechanisms.</p>