Executive functions in people with Down Syndrome across the lifespan: A systematic review and meta-analysis of longitudinal studies

People with Down Syndrome (DS) show deficits in executive functions (EF), yet their development across the lifespan remains poorly characterized. Central questions, whether EF improves into adulthood, peaks or plateaus, and when decline begins, have been difficult to answer due to small, heterogeneous, and mostly cross-sectional studies. Clarifying this course is essential for understanding how EF develops under atypical neurobiological constraints. We conducted the first meta-analysis of longitudinal EF data in DS, synthesizing 30 studies comprising 1567 individuals aged 4–64 years to examine mean-level change and rank-order stability. Effect sizes were calculated as standardized mean change per year (Cohen's d ) and test–retest correlations across working memory/short-term memory (WM/STM), inhibition, flexibility, and higher-order EF. Results revealed a non-linear EF trajectory, with significant increase during childhood ( d year = 0.155, 95% CI[0.085;0.225]) and decline beginning in the fourth decade ( d year = −0.072, 95% CI[−0.116;-0.029]). Effects in late adolescence and early-to-mid adulthood were small and not statistically significant. These findings align with atypical frontal lobe maturation and early-onset neurodegeneration in DS and suggests that early neurodevelopmental differences impose constraints that shape EF trajectories across life. Rank-order stability was high ( r = 0.65–0.79), indicating preserved relative standing over time and pointing to early consolidation of EF profiles. However, the lack of DS-specific tasks posed a key issue, with 52% of measures showing floor and 48% ceiling effects. This study provides the first lifespan model of EF development in DS, quantifies change magnitude, establishes benchmarks for interventions and highlights conceptual and methodological priorities for future research.