Abstract
Background: Dynamic cerebral autoregulation (dCA) remains intact in both ageing and dementia, but studies of neurovascular coupling (NVC) have produced mixed findings.
Objective: We investigated the effects of task-activation on dCA in healthy older adults (HOA), and patients with mild cognitive impairment (MCI) and Alzheimer’s Disease (AD).
Methods: Resting and task-activated data from thirty HOA, twenty-two MCI, and thirty-four AD were extracted from a database. The autoregulation index (ARI) was determined at rest and during five cognitive tasks from transfer function analysis. NVC responses were present where group-specific thresholds of cross-correlation peak function and variance ratio were exceeded. Cumulative response rate (CRR) was the total number of positive responses across five tasks and two hemispheres.
Results: ARI differed between groups in dominant (p=0.012) and non-dominant (p=0.042) hemispheres at rest but not during task-activation (p=0.33). ARI decreased during language and memory tasks in HOA (p=0.002) but not in MCI or AD (p=0.40). There was a significant positive correlation between baseline ARI and CRR in all groups (r=0.26, p=0.018), but not within sub-groups.
Conclusion: dCA efficiency was reduced in task-activation in healthy but not cognitively impaired participants. These results indicate differences in neurovascular processing in healthy older adults relative to cognitively impaired individuals.
Keywords: Autoregulation index, dementia, cognitive impairment, healthy older adults, cerebral blood flow, cognition.
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