Gender Differences in Age of ASD Diagnosis and Social Characteristics of Children with ASD: From a US National Registry

Background:  

The male to female ratio in Autism Spectrum Disorders (ASD) is large and has remained consistent over several decades. Some studies indicate that the trajectory of ASD development may be different between males and females, including diagnostic age and core symptoms. But only few large sample studies address the different characteristics of social responsiveness in male and female children with ASD. 

Objectives:  

1. To explore the trend of gender differences in the age of first ASD diagnosis.

2. To measure how ASD symptom severity varies by gender.

Methods:  

Data for this study were generated from the Interactive Autism Network (IAN), a national web-based family-powered registry for ASD in the US. Registry data for the target population was collected from November 2006 to January 2013 for 15,644 under-18 children with ASD. Age of first ASD diagnosis was collected for 9,932 children, and a completed Social Responsiveness Scale (SRS) was appropriately scored for 5,103 children. Two sample t-tests were performed to compare age means in different gender groups, and a chi-square test was performed to assess whether gender rate differences are significant according to different diagnostic year, first diagnosis age, ASD diagnosis categories, and ASD symptom severity in different SRS domains characterized social responsiveness. 

Results:  

The male to female ratio in the target population was 4.54:1, similar to the US CDC ASD surveillance network report of 2014. The mean age of first diagnosis of both Asperger’s Syndrome (AS) and PDD-NOS was significantly different in females versus males (AS: F 7.6 ±3.4, M 7.1 ±3.0, p<0.01); PDD-NOS: F 4.0 ±2.5), M 3.8 ±2.3), p=0.031). Later we stratified children with verified first diagnostic age into four age groups (year 0-5, 5-10, 10-15, and 15-18). It demonstrated a trend of increasing female:male ratio in age of first diagnosis (p=0.02), with significant differences in both AS and PDD-NOS (AS: p<0.01; PDD-NOS: p=0.036). For those with completed SRS’s, females struggled more on social cognition (p<0.05), while males had more severe autistic mannerisms (p<0.01). In addition, males aged 10 to 15 had more significant difficulties with social awareness and social communication compared to female in this age range (p<0.05). In comparing year of registry enrollment, there was a trend of increased proportion of female children with ASD (p=0.02). The percentage of female children with ASD was significantly increased over time (p<0.05) in comparing early registrants (2006-2009) to later (2010-2013).

Conclusions:  

Many causes may lead to a delay in ASD diagnosis in female children with ASD, such as differing natural developmental trajectory, or professional or family under-awareness of ASD symptomatic differences in young female children. This study suggests that boys have more difficulties in social awareness and communication, and girls in social cognition. This may contribute to a later diagnosis in girls. With increased public and family awareness, there appears to be a trend of increased ASD recognition in girls. Future research on gender differences should compare different symptomology. Gender-specific risk factors should be taken into account in identification of ASD, especially for females.