Trends in the age-standardized prevalence of neurodevelopmental disorders in South America, 1990-2023.

Background: Neurodevelopmental disorders (NDDs) are substantial burdens for individuals and health systems; yet, their long-term epidemiology in South America is poorly characterized. Objective: To describe the trends from 1990 to 2023 in the age-standardized prevalence rates (ASPRs) of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and idiopathic developmental intellectual disability (IDID) across 12 South American countries using Global Burden of Disease (GBD) 2023 estimates. Methods: Country-specific annual ASPRs and 95% uncertainty intervals (95%UIs) were obtained from the GBD 2023. Sex-stratified ASPRs were used to calculate male-to-female ratios (MFRs) and summarize long-term sex disparities. Temporal trends were assessed using the average annual percent change (AAPC) from log-linear regression for each country. Results: In 2023, the ASPRs ranged from 0.57 to 1.06% for ASD, from 1.00 to 2.55% for ADHD, and from 0.42 to 0.54% for IDID across countries. Between 1990 and 2023, the ASD ASPRs increased in all countries, with AAPCs from +0.35%/year (Paraguay) to +0.79%/year (Chile). The ADHD ASPRs showed little net change, with AAPCs from -0.10%/year (Argentina) to +0.39%/year (Brazil). And the IDID ASPRs declined consistently, with AAPCs from -0.79%/year (Bolivia) to -0.30%/year (Suriname). Sex differences in ASPRs were large and persistent for ASD and ADHD, but small for IDID. The MFR trajectories suggested a slight widening of the ASD male-female gap, largely stable ADHD disparities, and minimal variability for IDID. Conclusion: Over 3 decades, the ASD ASPRs rose modestly, the ADHD ASPRs were broadly stable, and the IDID ASPRs declined across South America. The GBD 2023 estimates point to enduring diagnostic and structural inequities and to the need for strengthened surveillance and more equitable access to developmental assessment.