Bayesian prevalence of autism and unmet special education needs in Chile in a sample of three million school-age children.

Autism spectrum disorder prevalence estimates in Latin America have been limited by a lack of reliable data. This cohort study aimed to estimate autism spectrum disorder prevalence in Chile by linking school registries with electronic health records. Probabilistic data linking was conducted between the 2021 Chilean school registry and 2003-2015 health records from the Araucania Sur Health Service. Bayesian prevalence estimation was used, considering variables such as age, sex, immigration status, ethnicity and rurality. Autism spectrum disorder prevalence across 29 health services was analysed for students aged 6 to 18 years. Regression models assessed unmet needs for special education services, validated using Araucania Sur Health Service health records. The study included 3,056,306 pupils (51.34% boys; mean age 11.6 years), with 14,549 having autism spectrum disorder. The national standardized school prevalence was 0.46%. Boys had 6 times higher odds of receiving special education services support than girls. In Araucania Sur Health Service, the adjusted clinical prevalence from health records was 1.22%. The Bayesian projected national autism spectrum disorder prevalence was 1.31%. This study, the largest of its kind in Latin America, revealed a higher autism spectrum disorder prevalence than previously reported, with one in 76 children affected. Disparities were observed across sex, ethnicity and health services.Lay abstractThis project tried to understand how many children in Chile are affected by autism, as reliable data have been lacking not only in Chile but across much of Latin America. To do this, we carried out the largest autism prevalence study ever conducted in the region. We linked national school records from 2021 with over a decade of health records (2003-2015) from the Araucanía Sur Health Service in southern Chile. This allowed us to examine data from more than three million students aged 6 to 18 years across 29 health services. Our results revealed that around one in every 76 children may have autism - almost 3 times higher than what was reported in schools alone. We also found that boys were 6 times more likely than girls to receive special education support. Using advanced statistical modelling, we estimated a national autism prevalence rate of 1.31%. Importantly, we discovered disparities in diagnosis and access to support based on sex, ethnicity, immigration status and whether a child lived in a rural or urban area. These findings highlight the need for more inclusive and equitable approaches to autism identification and care across Chile. This research not only helps to fill a major data gap but also offers a model for how countries with limited resources can use existing administrative data to improve public health planning and educational support for children with autism.