Altered neurovascular coupling in mild cognitive impairment and Alzheimer's disease: Associations with polysomnography-derived sleep parameters and cognition

BackgroundNeurovascular coupling (NVC) reflects the coordination between neuronal activity and cerebral perfusion, and impaired NVC has been implicated in cognitive decline.ObjectiveTo characterize imaging-based NVC-related measures at global and regional levels and examine their associations with polysomnography-derived sleep parameters and cognitive performance in mild cognitive impairment (MCI) and mild Alzheimer's disease (AD).MethodsTwenty-one healthy controls (HC), 21 individuals with MCI, and 22 patients with mild AD underwent arterial spin labeling, resting-state functional MRI, overnight polysomnography, and neuropsychological assessment. Global cerebral blood flow-regional homogeneity (CBF-ReHo) coupling and regional CBF/ReHo ratios were quantified as imaging-based NVC-related measures. Group comparisons, partial correlations, exploratory logistic regression models, and apnea-hypopnea index (AHI)-adjusted sensitivity analyses were performed.ResultsGlobal CBF-ReHo coupling was significantly lower in both MCI and mild AD than in HC. Voxel-wise analyses identified lower CBF/ReHo ratios in the left inferior temporal gyrus in MCI and the right fusiform gyrus in mild AD, with the fusiform finding attenuated after AHI adjustment. N3 sleep percentage was positively associated with global CBF-ReHo coupling in mild AD and with regional CBF/ReHo ratios in group-specific ventral temporal clusters; these regional ratios were positively associated with Montreal Cognitive Assessment in MCI and Mini-Mental State Examination in mild AD. Exploratory logistic models using global CBF-ReHo coupling showed preliminary discrimination between cognitively impaired participants and HC but limited MCI-AD discrimination.ConclusionsThese findings suggest a potential sleep-neurovascular link in cognitive impairment and warrant longitudinal and interventional studies to clarify the role of NVC-related imaging measures.