Early sensory differences in toddlers at elevated likelihood for autism and association with later autistic traits: a prospective cohort study.
BACKGROUND As a core diagnostic criterion for autism spectrum disorder (ASD), sensory differences may have profound implications for the quality of life among autistic individuals. However, little is known about the developmental trajectories of sensory features in toddlers at elevated likelihood (EL) for ASD. The associations between early sensory patterns and later autistic traits also remains unclear. METHODS A total of 127 toddlers were enrolled in a China cohort study. At 24 months, 125 toddlers were classified into three groups: EL toddlers diagnosed with ASD (EL-ASD, n = 18), EL toddlers not meeting diagnostic criteria for ASD (EL-nonASD, n = 38), and low likelihood toddlers without ASD (LL, n = 69). Prospective longitudinal assessments of sensory patterns were conducted using the Toddler Sensory Profile-2 (TSP-2). Sensory patterns were compared among groups from 12 to 24 months by Linear Mixed-effects Models and Bonferroni post-hoc comparisons. The associations between early sensory patterns and later autistic traits were also examined. RESULTS A significant group × time interaction for sensory sensitivity across 12-24 months (F = 9.87, p < 0.001), and a marked increase in sensory sensitivity in EL-ASD toddlers between 18 and 24 months (p < 0.001). EL-ASD toddlers exhibited significantly higher sensory registration, auditory processing and touch processing scores at 12 months compared to LL group. Elevated sensory registration scores at 12 months were positively associated with social affect (B = 0.14, p = 0.036), restricted repetitive behaviors (RRBs; B = 0.12, p = 0.003), and total scores (B = 0.25, p = 0.005) at 24 months among EL-ASD toddlers. Additionally, elevated sensory avoiding scores at 18 months were positively associated with social affect (B = 0.33, p = 0.045) and total scores (B = 0.30, p = 0.046) at 24 months. CONCLUSIONS Distinct sensory patterns emerge by 12 months in elevated likelihood toddlers later diagnosed with autism, with sensory sensitivity increasing significantly between 18 and 24 months. Notably, early hypo- and hyper-responsivity predict later social communication difficulties and RRBs, suggesting that sensory differences may exert a "cascading effect", thereby contributing to autistic outcomes. CLINICAL TRIAL NUMBER www.chictr.org.cn/; No: ChiCTR2100049811; Date:2021.08.10.