Key result
Lower flow-mediated dilation is linked to elevated cerebral amyloid-β burden, averaging ~3 percentage points lower.
Why the study?
Vascular health is closely related to Alzheimer's disease, but vascular function measured by flow-mediated dilation or pulsatility index is poorly characterized in those at risk for Alzheimer's disease.
Is impaired peripheral (brachial artery FMD) and central (middle cerebral artery PI) vascular function associated with elevated cerebral amyloid-β burden and white matter lesion volume in cognitively normal older adults?
Cross-Sectional (n=83)
Study personnel performing the TCD and FMD data collection were blinded to the Aβ status of participants
No
Is impaired peripheral (brachial artery FMD) and central (middle cerebral artery PI) vascular function associated with elevated cerebral amyloid-β burden and white matter lesion volume in cognitively normal older adults?
Impaired peripheral endothelial function measured by brachial artery flow-mediated dilation is independently associated with higher cerebral amyloid-β burden in cognitively normal older adults, linking peripheral vascular health to preclinical Alzheimer's disease pathology.
Answers are grounded in this paper and cite their sources.
Impaired brachial FMD should not yet change practice; hypothesis-generating for vascular contributions to preclinical amyloid burden.
BACKGROUND: Vascular health is closely related to Alzheimer's disease (AD). Vascular function measured by flow mediated dilation (FMD) or pulsatility index (PI) can be used as marker of peripheral and central vascular health but is poorly characterized in those at risk for AD. OBJECTIVE: To assess the relationship of peripheral and central vascular function with amyloid-β (Aβ) and white matter lesion burden among cognitively normal older adults. METHODS: We enrolled participants 65 years of age and older. Using Doppler ultrasound, we assessed brachial artery FMD, and middle cerebral artery (PI). Global Aβ burden, quantified using [18F] Florbetapir PET imaging, and white matter lesion volume (WML) were used as measures of AD pathology and vascular brain injury. RESULTS: After adjusting for age and cardiovascular risk factors, the data (n = 83) showed a negative association between FMD and Aβ burden (β= -0.03, p < 0.001). FMD at a cut-off of 4.45% had 88% specificity and 75% sensitivity to elevated Aβ (AUC = 0.86, 95% CI: 0.77-0.95). FMD was not related to WML volume (p = 0.8), and PI was unrelated to Aβ burden or WML volume (0 > 0.4). CONCLUSIONS: Among cognitively normal older adults, blunted peripheral vascular function, as measured by brachial artery FMD, is associated with Aβ burden. These findings provide support for further exploration into the pathophysiological relationship of vascular health and AD risk as measured by Aβ.
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Liu et al. (2019) conducted a cross-sectional in Cognitively normal older adults at risk for Alzheimer's disease (evaluated for amyloid-β burden and vascular function) (n=83). Brachial artery flow-mediated dilation (FMD) and middle cerebral artery pulsatility index (PI) vs. Elevated global amyloid-β burden (>1.1 SUVR, n=20) vs non-elevated amyloid-β burden (≤1.1 SUVR, n=63) was evaluated on Global cerebral amyloid-β (Aβ) burden quantified using [18F] Florbetapir PET standardized uptake value ratio (SUVR) (β = -0.03 (for FMD association with Aβ burden); AUC 0.86 for FMD cutoff 4.45%, 95% CI 0.77-0.95, p=<0.001). Brachial artery flow-mediated dilation was negatively associated with cerebral amyloid-β burden (β = -0.03, p < 0.001) and was significantly lower in older adults with elevated amyloid-β (3.8% vs 6.8%, p < 0.01).
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