Regional structural-functional coupling alterations associated with subjective sleep quality in young adults

Poor sleep quality is associated with adverse behavioural and brain-related outcomes, yet the neurobiological mechanisms remain incompletely understood. Because sleep is thought to support synaptic renormalization and network reorganization, structural-functional connectivity (SC-FC) coupling-indexing the correspondence between the brain's anatomical scaffold and resting-state functional interactions-may provide complementary sensitivity beyond structural or functional connectivity alone.

We analysed multimodal MRI data from 1037 adults in the Human Connectome Project. Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI), and Mini-Mental State Examination (MMSE) total score was included as a coarse exploratory measure. Regional SC-FC coupling was quantified as the region-wise correspondence between diffusion-derived structural connectivity and resting-state functional connectivity profiles. We compared coupling between poor sleepers (PSQI>5) and good sleepers (PSQI≤5). We further used linear support vector regression (SVR) with leakage-controlled nested cross-validation to explore multivariate coupling patterns associated with PSQI. Finally, in secondary exploratory analyses, we tested whether regional coupling showed statistical indirect effects in the PSQI-MMSE association.

Compared to good sleepers, poor sleepers exhibited reduced SC-FC coupling in frontoparietal and default-mode regions, alongside increased coupling in temporal subregions. SVR revealed a statistically significant but weak out-of-sample association between coupling features and PSQI, with negligible variance explained at the individual level. Additionally, coupling in frontal subregions showed small indirect effects in the PSQI-MMSE association.

Regional alterations in structure-function alignment were associated with subjective sleep quality, highlighting SC-FC coupling as a mechanistically interpretable marker of sleep-related brain differences. Further validation in clinical and longitudinal cohorts is needed.