Postural sway dynamics in adults across the autism spectrum: a multifactor approach

Motor challenges are highly prevalent within autism, and increased postural sway has been consistently demonstrated in autistic youth. However, the extent to which sway anomalies extend into adulthood remains understudied. This study aimed to investigate whether increased postural sway is altered in autistic adults compared to neurotypical controls using established sway metrics including sway area and path, as well as rambling-trembling decomposition—an approach that differentiates the postural sway signal into central and peripheral nervous system components. 49 adults with autism spectrum conditions (ASC) and 94 neurotypical controls (NC) participated in a postural sway task on a force platform with manipulations of visual input and stance width. Traditional geometric methods (sway area and path), the spatial characteristics of the body’s adjustment to maintain balance, were measured. As resulting sway measures often covary, multiple factor analysis (MFA) was applied to reduce the measures into distinct, non-redundant dimensions that simplified the data. Group comparisons were completed across these different levels of analysis. We observed increased sway path and medio-lateral trembling in ASC compared to NC (p < 0.05). Significant group by vision interactions revealed that ASC sway increases were more apparent in eyes-open conditions for sway area and rambling and trembling in the anterior-posterior plane (p < 0.01), possibly suggesting differential sensory reweighting of visual input by ASC, or difficulties with multisensory integration. MFA revealed two key dimensions. A fast frequency dimension, linked to peripheral processes, explained most of the overall variance (62.9%) and captured more variance in the ASC group than in NC. A slower frequency dimension, linked to central processes, explained 8.0% of the variance. Order of sway conditions was consistent among all participants, so it is possible that participant fatigue influenced later sway conditions. Building upon previous research finding increased postural sway in autism, we found that combining multiple approaches collectively suggest the critical role of peripheral contributions and visual input in postural sway in autism. Fast-frequency processes that are peripherally-driven may be of particular importance in sway in autistic adults, and should be prioritized in future research to better understand balance performance in autism.