Sleep Disturbances Differentially Associated With First and Second Language Receptive Vocabulary in Autistic Children

The present study aimed to investigate the relationship between sleep behaviors and receptive vocabulary in bilingual autistic children. While the facilitating role of sleep in language development is well established in typically developing (TD) children, autistic children commonly experience both sleep disturbances and language difficulties. However, little is known about the relationship between these factors, particularly with respect to second language (L2) vocabulary development. This cross-sectional study addresses this important and underexplored issue.

We examined sleep behaviors in 36 autistic children and 40 typically developing (TD) children (aged 5-10 years) in Hong Kong using a parent-administered sleep questionnaire, the Children's Sleep Habits Questionnaire (CSHQ). Receptive vocabulary in the first language (L1) and L2 receptive was assessed using standardized tests.

Autistic children exhibited significantly greater sleep disturbances than their TD peers, including more frequent night wakings and parasomnias (e.g., bedwetting, sleep talking, and teeth grinding). Importantly, sleep disturbances in autistic children were adversely associated with L2 vocabulary scores (daytime sleepiness: B = -2.26, p = 0.019), but less so with L1. Autistic children who experienced greater daytime sleepiness showed lower L2 vocabulary scores, likely reflecting reduced attention and working memory in the cognitively demanding context of L2 learning.

These findings highlight the association between sleep behaviors and L2 vocabulary in autistic children. Future longitudinal and intervention-based research should further investigate the directionality of these relationships.