Abstract P61: Pulsatility Index Outperforms Conventional Imaging Markers in the Association With Cognition in Community Subjects

Abstract

Increase in pulsatility index (PI), measured by the transcranial Doppler (TCD), correlates with cognitive impairment and is associated with progression of non-demented patients into Alzheimer’s disease (AD) with dementia, suggesting that increase in small vessel resistance is a critical marker of cognitive decline. No study compared PI and MRI markers for small vessel disease or AD that have been shown to be associated with worse cognitive functions. The objectives of this study include: (i) compare PI against conventional MRI markers in its association with cognition, and (ii) investigate the association of PI and cognition in the presence of vascular risk factors. We measured clinical data and PI in the middle cerebral artery in 331 stroke- and dementia-free community subjects. General cognition was assessed using Hong Kong-Montreal Cognitive Assessment. Conventional imaging markers (including lacunes, white matter hyperintensities (WMH), brain parenchymal fraction (BPF), cerebral microbleeds, Alzheimer’s Disease Resemblance Atrophy Index (ADRAI)) were assessed by MRI. Linear regression models were used to compare the sensitivity of PI against conventional MRI markers (including WMH, BPF, ADRAI, lacune and cerebral microbleeds count), with age and years of education entered as covariates. PI was negatively associated with cognition (standardised b=-0.122, p=0.01). PI outperformed (standardised b=-0.118, p=0.012) other imaging markers and contributes to 1.1% change in the variance. PI was associated with higher systolic blood pressure (standardised b=0.122, p=0.028), and level of triglyceride (standardised b = 0.126, p = 0.021). To conclude, PI is associated with cognition, higher levels of blood pressure and triglycerides, suggesting a vascular component in cognitive decline. PI outperforms conventional MRI markers in the association with cognition in community subjects without dementia. As TCD is non-invasive, portable with a lower cost than MRI, PI may serve as a simple marker in monitoring cerebral small vessel resistance and cognition in older people.