Altered glymphatic system measures and functional network connectivity in autism spectrum disorder: A longitudinal study examining associations with prognosis

AIM: Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social deficits and repetitive behaviors, yet prognostic biomarkers remain elusive. This study investigated the interplay between glymphatic function and functional network connectivity (FNC) in ASD and their longitudinal associations with clinical outcomes. METHOD: This combined cross-sectional and two-year prospective longitudinal study included 50 ASD children and 50 controls. Glymphatic function was assessed using the along the perivascular space (ALPS) index and global blood-oxygen-level-dependent to cerebrospinal fluid (gBOLD-CSF) coupling, alongside FNC analysis. RESULTS: Cross-sectionally, ASD participants showed significantly reduced ALPS index, gBOLD-CSF coupling, and widespread FNC reductions. Longitudinally, among the 40 ASD participants who completed follow-up, glymphatic function increased over time. Greater increases in ALPS were correlated with greater reductions in ADOS-CSS. In the symptom-improved subgroup, four FNC connections (including DMN-DAN) increased over time. In contrast, no consistent pattern was found in the non-improved group. Baseline inter-network connectivity measures were associated with ADOS-CSS reduction in univariate analyses, but the multivariate model was not significant. Mediation analysis showed an indirect association between baseline gBOLD-CSF coupling and long-term ADOS-CSS reduction via DMN-DAN FNC reduction (indirect effect = -0.22, 95% CI [-0.42, -0.07]). CONCLUSION: These findings indicate that glymphatic function and FNC are altered cross-sectionally and improve longitudinally in parallel with symptom changes in ASD and suggest that baseline gBOLD-CSF coupling is indirectly associated with long-term clinical improvement through DMN-DAN connectivity. Together, these results highlight the potential of glymphatic and functional connectivity measures as prognostic imaging markers in ASD.