Abstract:Objective To investigate the age of diagnosis of autism spectrum disorder (ASD) and the factors influencing the age of diagnosis in children. Methods A retrospective analysis was performed for the clinical data of 1691 children who visited in the Children's Hospital of Chongqing Medical University for the first time and were definitely diagnosed with ASD between February 2011 and July 2017. A multiple linear regression model was used to identify the factors influencing the age of diagnosis of ASD. Results The ASD children had a mean age of 35±17 months (range 9-175 months) at diagnosis. Of all 1691 children, the children who received a diagnosis of ASD at the age of 24-35 months accounted for the highest proportion (46.13%, 780/1691), followed by those at the age of ≥ 36 months (33.41%, 565/1 691). The multiple linear regression analysis showed that the children who had language disorders or lived in the main urban area or whose parents had a high education level had a younger age at diagnosis than other children (P < 0.05). Conclusions Most ASD children have an age of 24-35 months at diagnosis. The age of diagnosis of ASD is associated with children's symptoms, living area, and parents' education level.