Prevalence of autism spectrum disorder in children: complete census of a Brazilian municipality.

The prevalence of autism spectrum disorder (ASD) has been an issue of great concern worldwide, leading to attempts to estimate prevalence based on population samples, including those conducted in Brazil. No epidemiological study in this field has covered an entire population. We aimed to determine the prevalence of ASD in a Brazilian population. This complete census was conducted from March to December 2024 in the municipality of Coxilha, Rio Grande do Sul State, Brazil. All children aged 2.5 to 12 years were screened using the Mini-TEA scale. Children with a score above the 100% sensitivity threshold (> 4 points) were then examined by a neurologist with experience in ASD to establish the diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders. Demographic data were obtained. There was no refusal to participate. Among the 475 children (240 boys and 235 girls), we found 16 ASD cases (15 boys and 1 girl), i.e., 1 in 30 children (1 in 16 boys and 1 in 235 girls), yielding an overall prevalence of 3.36% (6.25% among boys and 0.42% among girls). All ASD cases had also been diagnosed by other professionals. Only one child's previous diagnosis of ASD was rejected. ASD showed a high prevalence and male predominance in this unprecedented complete census. The overall prevalence is similar to that reported in the United States but higher than previous Brazilian estimates. Further research is necessary to investigate etiological factors.