Spontaneous Cerebrovascular Reactivity at Rest in Older Adults with and without Mild Cognitive Impairment and Memory Deficits
- Engstrom, Allison C
- Advisor(s): Thayer, Julian F
Abstract
Background: Deficits in cerebrovascular reactivity (CVR) to experimentally-induced hypercapnia are observed in older adults with mild cognitive impairment (MCI), suggesting a role for CVR as a biomarker of vascular contributions to MCI. Spontaneous CVR at rest has also been studied without experimental induction of hypercapnia. The present study sought to determine whether spontaneous CVR in whole brain and medial temporal regions is associated with MCI and memory impairment.
Methods: Independently living older adults without history of clinical stroke, dementia or other major neurological or psychiatric disorder were recruited from the community. Participants underwent clinical interview, comprehensive cognitive testing, venipuncture for plasma Alzheimer’s disease (AD) biomarkers, and brain MRI. Pseudo-continuous arterial spin labeling MRI quantified whole brain perfusion during 5min of rest with simultaneous monitoring of end-tidal CO2 (ETCO2) levels. Spontaneous CVR maps were quantified as %∆CBF/∆ETCO2 at rest.
Results: A total of 161 older participants (mean age = 69.5 years; SD = 7.6; age range 55–89 years; 34.8% male) were studied. Spontaneous whole brain CVR was negatively associated with associated with age, [B = -0.41, 95% CI (-0.65, -0.17), p = 0.00096, but not MCI. Analysis of medial temporal regions revealed that spontaneous CVR in the parahippocampal gyrus (PHG) was significantly lower in participants with MCI compared to those who were cognitively unimpaired, t (148) = 2.90 95% CI (1.93, 10.46), p = 0.005. Participants with amnestic MCI also showed significantly lower spontaneous PHG CVR relative to cognitively unimpaired, t (134) = 3.055 95% CI (2.59, 13.29), p = 0.005. Decreased spontaneous PHG CVR was associated with worse memory composite z-scores, B = 0.26, 95% CI (0.56, 3.12), p =0.005. Findings remained consistent after controlling for AD biomarkers and vascular risk factor burden.
Conclusion: Deficits in spontaneous CVR at rest are observed in older adults with MCI, specifically in the PHG, and particularly in those with memory impairment. These findings further implicate medial temporal microvascular dysfunction in cognitive decline and memory impairment among older adults at risk for dementia, independent of AD pathophysiologic change. Spontaneous PHG CVR may be a useful marker for vascular contributions to memory decline.