Associations between awake-state cerebral hemodynamic activity and sleep quality: A longitudinal fNIRS study in young adults and implications for rehabilitation

Poor sleep quality is a significant public health challenge, particularly among young adults, and can impede recovery and rehabilitation. However, there is a lack of objective, field-deployable neurophysiological markers for widespread sleep health screening. This 4-month longitudinal study aimed to examine whether awake-state cerebral hemodynamic activity, measured using portable functional near-infrared spectroscopy (fNIRS), could serve as a neurophysiological correlate of sleep quality and a potential tool for monitoring rehabilitation progress. Eighty-six young adults underwent monthly assessments that included 24-channel fNIRS recordings (resting-state and N-back/Stroop tasks) and the Pittsburgh Sleep Quality Index (PSQI). Linear mixed-effects models (LMMs) were used to evaluate within-subject associations between hemodynamic indicators and PSQI scores, adjusting for socio-demographic and behavioral covariates. Increased oxyhemoglobin responses during the N-back task were significantly associated with higher PSQI scores (poorer sleep quality) across the frontal and precentral gyri ( β 1 = 0.28-0.36, P <.05). These associations were particularly robust for the PSQI subcomponents assessing daytime dysfunction and habitual sleep efficiency. Sex-stratified analyses revealed a marked disparity: associations were extensive and stronger in males ( β 1 = 0.37-0 . 54, P <.05), whereas only a single channel showed significance in females. These findings suggest that awake-state cortical hyperactivation, particularly peak oxy-Hb amplitude, serves as a reliable marker of poor sleep quality. Portable fNIRS offers a feasible, non-invasive tool for monitoring sleep health in clinical and rehabilitation settings, supporting early detection and tailored interventions to improve recovery outcomes. • Awake-state fNIRS detects sleep-related cortical hyperactivation in young adults • Fronto-motor oxy-Hb responses reflect functional cost of poor sleep quality • Task-evoked hemodynamics outperform resting measures for sleep monitoring • Daytime dysfunction and sleep efficiency show strongest neural correlates • Portable fNIRS enables scalable sleep health assessment in rehabilitation