Disrupted white matter microstructure in insomnia disorder: a diffusion kurtosis imaging study

Insomnia disorder (ID) is associated with neurocognitive dysfunction, but the underlying white matter microstructural abnormalities and their neurobiological mechanisms remain poorly characterized.

Diffusion kurtosis imaging (DKI) and tract-based spatial statistics were employed to compare white matter integrity between 30 ID patients and 30 age-matched healthy controls. Diffusion kurtosis and tensor parameters were analyzed to evaluate microstructural complexity and directional coherence.

ID patients exhibited extensively reduced radial kurtosis (RK) across critical white matter tracts, including the forceps minors, inferior fronto-occipital fasciculus and the left inferior longitudinal fasciculus. Moreover, ID patients exhibited reduced fractional anisotropy (FA) across white matter tracts, including the forceps minors, inferior fronto-occipital fasciculus and the anterior thalamic radiation. Step-wise regression analyses revealed that both RK and FA decreases were negatively correlated with insomnia duration (RK = 1.46-0.006 ∗ duration, p = 0.03; FA = 0.50-0.001 ∗ age - 0.001∗ duration, p < 0.001), suggesting progressive white matter degeneration with prolonged sleep disruption.

ID is linked to microstructural disintegration in emotion- and arousal-modulating white matter networks, with DKI parameters (particularly RK) demonstrating superior sensitivity to early pathological changes compared to conventional diffusion metrics. Despite these promising results, the cross-sectional design and relatively small sample size warrant caution, and future longitudinal studies in larger cohorts are needed to confirm these findings. These findings advance the characterization of insomnia-related neuropathology and highlight the potential of DKI as a biomarker for monitoring disease progression and guiding targeted interventions.