Diverging trends in neurodevelopmental disorder diagnoses among children aged below 16 years in Kazakhstan (2014-2024): a national registry study.

Introduction: Neurodevelopmental disorders are increasingly straining health systems. However, how these disorders are distributed across populations, or whether their occurrence is increasing, is still not fully understood. This study examined registry-based prevalence, temporal trends, geographic variation, and associated systemic factors in a Central Asian setting. Methods: We analysed national electronic health-registry data from Kazakhstan for children aged ≤15 years from 2014 to 2024 using a repeated cross-sectional design. The register is a prevalent "on-the-register" stock registry, and the unit of analysis is the registry record per child-year; the pooled total of 214,904 records therefore represents child-year observations rather than unique children. Annual registry-based prevalence was calculated against official population denominators. Temporal trends were modelled with negative-binomial regression and summarized as annual percent change (APC) and segmented regression; regional differences and associated factors were examined with Bayesian hierarchical and mixed-effects models. Results: Among the 214,904 registered records, intellectual disability made up the largest share at 60.8%, followed by autism spectrum disorder at 20.9%, other developmental disorders at 17.1%, and attention-deficit/hyperactivity disorder at 1.1%. Registry-based ASD prevalence rose steeply from 16.8 to 190.5 per 100,000 (APC +27.0%/year), accelerating after the 2021 policy expansion. In contrast, other developmental disorders (-7.8%/year) and ADHD (-10.2%/year) declined, while intellectual-disability prevalence remained essentially stable (APC -0.7%/year, not statistically significant). The decline in the share of intellectual disability therefore reflects a compositional shift driven by the increase in ASD. Marked geographic differences were observed, with higher registry-based ASD prevalence in metropolitan areas and northern and eastern regions, together with strong differences related to the diagnosing specialist. Discussion: These patterns indicate that registered neurodevelopmental diagnoses in Kazakhstan are shaped not only by epidemiology but heavily by changing diagnostic practices, specialist availability, reimbursement policy, and the organization of services. Registry-based estimates should therefore be interpreted as measures of ascertainment rather than of true population prevalence. This study offers a national perspective on registry-based trends in developing regions and emphasizes the importance of systemic factors when planning services and estimating the true burden of these disorders.