Age-Specific Time Trends in Incidence Rates of Autism Spectrum Disorder Following Adaptation of DSM-5 and Other ASD-Related Regulatory Changes in Israel

We analyzed data on 879,029 children born in 1999-2017 from a large Israeli health fund to evaluate time-trends in incidence of autism spectrum disorder (ASD). This included examining possible effects associated with the adaptation of the DSM-5 criteria for ASD, and the implementation of regulatory changes affecting eligibility for ASD-related stipends and services. ASD cases were ascertained based on electronic medical records review, with complete verification of ASD case status. Results indicated a substantial increase in ASD incidence rate (IR) over time that was overall not appreciably affected by the above changes. Cumulative incidence through age 8 rose from 0.46% (boys: 0.73; girls: 0.18) in 2007 to 1.30% (boys: 2.12; girls: 0.45) in 2018. Age-specific analyzes indicated that the largest increase in IR occurred in toddlers and preschool children, with a more modest increase at older age groups. Results suggest that the rise in early diagnosed ASD does not stem from a downward shift in the distribution of ages at first diagnosis, but rather from early detection of cases not previously diagnosed. Findings highlight the need to expand research aimed at identifying exogenous factors that may underlie the rise in incidence, and to evaluate factors that may contribute to late diagnosis of some cases. Lay Summary In an analysis of nearly 900,000 Israeli children born in 1999-2017, we found that the incidence of autism spectrum disorder (ASD) increased significantly over time, especially among toddlers and preschool children but also at older age groups. We additionally observed that changes affecting diagnostic criteria for ASD and eligibility for ASD-related services did not appreciably affect these trends. Results highlight the need to continue research aimed at identifying factors causing this increase and reasons contributing to late diagnosis of some cases.