Distributions of SRS-Measured Autistic Traits in a Taiwanese Population of Children Aged 6-8 Years

Background: It is well accepted that Autism Spectrum Disorder (ASD) represents one end of a larger spectrum of quantitative impairment that is continuously distributed in the general population. The Social Responsiveness Scale (SRS) is an instrument that characterizes quantitative impairments in social awareness, cognition, communication, motivation, and repetitive behavior/restricted interests that define ASD, and provides a subtler characterization of individual symptoms than using traditional classification systems. This tool is particularly feasible for assessing autistic traits in large, population-based studies because it can quantify the spectrum of dimensional impairments of ASD. Implementing the SRS in a large population will allow it to be utilized across different settings and against different norms and subgroups such as gender, age, or racial/ethnical background.

Objectives: To examine the distributions and sex difference of SRS item scores by its five dimensions in a Taiwanese population of children aged 6-8 years. 

Methods: Caregiver-reported SRS data were collected by an epidemiologic autism study conducted in Pingtung Taiwan. A total of 2891 primary caregivers completed the SRS for 1428 males and 1546 females. Children whose sex was not reported were excluded from this analysis. Distributions of mean item raw scores were examined by SRS domains and by child sex to describe the population-baseline, and those whose total raw scores were above the cut-point. As recommended in the literature, a raw score of >=70 in males and >=65 in females is a cut-point that provides evidence for the presence of an ASD in Western countries. Of all the included participants, 172 males and 185 females met these recommended cut-points. T-tests were conducted to compare the mean item raw scores between males and females.  

Results: As expected, males were rated with higher raw scores on the majority of SRS items (55 out of 65) compared to females in the general population. Significant sex differences were observed for the majority of items in the domains of Social Awareness, Social Communication, and Autistic Mannerisms (AM). Similar score distribution patterns were shown among children who met the recommended cut-points. Notably, the magnitude of item score differences between males and females who met the cut-point is particularly paramount in the AM domain, being between 3 to 4 times that of sex differences in the general population. 

Conclusions: Our findings indicate male children in this Taiwanese population have higher item SRS scores than female children, in the general population and in those at high risk of ASD. Higher SRS scores in males have been reported in clinical-based studies, our findings are the first to confirm such a distribution in the general population. We found that sex differences particularly stand out in the AM domain, in both the general population and in children at high risk of ASD. AM may play a key role in interpreting the sex disparity of ASD diagnoses. As there are no autism epidemiologic studies of this kind, our study provides first insights on how autistic traits are distributed in general populations (population baseline) and in those at high risk of ASD.