New research from the University of Southern California suggests that subtle declines in brain blood flow and oxygen delivery may be early indicators of Alzheimer's disease. The study, published in Alzheimer's and Dementia, used noninvasive scans to connect vascular health with amyloid plaques and hippocampal shrinkage. These findings highlight the role of brain circulation in the disease process beyond traditional markers like amyloid and tau.
Researchers at the Mark and Mary Stevens Neuroimaging and Informatics Institute at the Keck School of Medicine of USC conducted a study on older adults, both with and without cognitive impairment. The work, detailed in the journal Alzheimer's and Dementia: The Journal of the Alzheimer's Association, explored how brain blood flow and oxygen use relate to established Alzheimer's signs.
The team employed transcranial Doppler ultrasound to measure blood velocity in major brain arteries and near-infrared spectroscopy to assess oxygen delivery to cortical tissue. By applying mathematical modeling, they created indicators of cerebrovascular function, which adjust to fluctuations in blood pressure and carbon dioxide.
Participants with vascular function similar to cognitively healthy adults showed lower amyloid levels and larger hippocampi, both associated with reduced Alzheimer's risk. Those with mild cognitive impairment or dementia exhibited weaker vascular performance.
"Amyloid and tau are often considered the primary players in Alzheimer's disease, but blood flow and oxygen delivery are also critical," said Amaryllis A. Tsiknia, the study's lead author and a USC PhD candidate. "Our results show that when the brain's vascular system functions more like it does in healthy aging, we also see brain features that are linked to better cognitive health."
Meredith N. Braskie, PhD, the senior author and assistant professor of neurology, noted: "These vascular measures are capturing something meaningful about brain health. They appear to align with what we see on MRI and PET scans that are commonly used to study Alzheimer's disease."
Arthur W. Toga, PhD, director of the Stevens INI, added: "These findings add to growing evidence that Alzheimer's involves meaningful vascular contributions in addition to classic neurodegenerative changes."
The methods are less invasive and costly than MRI or PET scans, potentially enabling broader screening. However, the study provides a cross-sectional view and does not prove causation. Long-term research is underway to monitor if vascular changes predict cognitive decline.
The study was supported by the National Institutes of Health and the National Institute on Aging.
