Ontario cohort finds widening socioeconomic and immigration disparities in autism diagnoses

Researchers examined trends in autism spectrum disorder (ASD) diagnoses in Ontario, Canada, where universal health care provides a setting to assess persistent inequities. The retrospective cohort included 2,319,302 children born during 2002-2020, linked to maternal health, immigration, and census data. Children were followed from age 1 year until ASD diagnosis, death, out-migration, or April 2020. ASD was identified using a validated administrative algorithm; outcomes included diagnosis rates and cumulative incidence at age 8 years.

Overall, 29,374 children (1.3%) met ASD criteria. Diagnosis increased by 10% per successive birth cohort (95% CI, 10%-11%). By the 2012 birth cohort, diagnosis was 2.2-fold higher in the most versus least deprived neighborhoods and 2.0-fold higher in the most versus least ethnically diverse areas. Diagnosis was lower in rural than urban regions and 1.4-fold higher among children of immigrant mothers, with the highest rates among mothers from low- and middle-income regions.

Maternal diabetes, severe maternal morbidity, and prematurity were more common in marginalized populations, and disparities in maternal diabetes widened over time. The findings highlight uneven diagnostic patterns despite universal coverage. However, administrative diagnoses do not distinguish differences in underlying ASD occurrence from differences in identification. The observational design cannot establish whether perinatal factors caused the disparities; the full text was unavailable for assessment.