Global, Regional, and National Burden of Idiopathic Developmental Intellectual Disability in Children and Adolescents: Findings From the Global Burden of Disease Study 2021

Background: Idiopathic developmental intellectual disability (IDII) remains an important contributor to childhood and adolescent disability, yet its global burden, long-term trends, and future patterns remain insufficiently characterized. Methods: Data on IDII among children and adolescents were obtained from the Global Burden of Disease 2021 database. From 1990 to 2021, prevalent cases, disability-adjusted life years (DALYs), age-standardized prevalence rate (ASPR), and age-standardized DALY rate (ASDR) were analyzed, together with estimated and average annual percentage changes. Analyses were stratified across location, age groups, and sex. Lead-attributable IDII-related burden was assessed using the comparative risk assessment framework. Bayesian age-period cohort modeling was used to predict IDII trends from 2022 to 2050. Results: Globally, the number of prevalent IDII cases increased from 80.0 million (95% uncertainty interval [UI]: 43.34–115.31 million) in 1990 to 88.3 million (95% UI: 47.15–129.17 million) in 2021, DALYs rose from 3.3 million (95% UI: 1.53–5.63 million) to 3.8 million (95% UI: 1.76–6.52 million), while ASPR decreased by 17.9% and ASDR by 13.7%, with significant long-term declining trends. The increase in crude prevalent cases primarily reflects population growth rather than a statistically supported increase in underlying disease risk. Low-middle sociodemographic index regions showed the greatest declines, whereas Australasia and Central Sub-Saharan Africa exhibited increasing trends. In 2021, the 5–9 and 10–14-year age groups accounted for a large proportion of the global burden. In addition, sex-specific patterns varied across regions and age groups. Lead exposure accounted for part of IDII-related DALYs in several high-burden regions within the comparative risk assessment framework. Projection analyses indicated that both ASPR and ASDR may continue to decline through 2050. Conclusions: The age-standardized burden of IDII among children and adolescents declined globally from 1990 to 2021, but substantial regional, age-specific, and sex-specific disparities persisted. Regions showing increasing trends, including Australasia and Central Sub-Saharan Africa, warrant continued surveillance. Future studies using standardized diagnostic protocols and individual-level exposure data are needed to clarify the contributions of diagnostic ascertainment and modifiable environmental risks to IDII burden.