Brain Blood Flow as Early Indicator of Alzheimer’s Risk

Subtle changes in how blood flows through the brain and delivers oxygen may be closely linked to the risk of developing Alzheimer’s disease, according to new research from the Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) at the Keck School of Medicine of USC. The findings suggest that assessing brain vascular health could offer a new avenue for early detection and potential prevention strategies.

Vascular Health and Alzheimer’s: A Growing Connection

Traditionally, Alzheimer’s disease research has focused on the buildup of amyloid plaques and tau tangles in the brain. However, this new study, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, highlights the critical role of cerebrovascular function. Researchers found that measures of brain blood flow and oxygen levels were associated with amyloid plaque buildup and shrinkage of the hippocampus, a brain region vital for memory.

“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, lead author of the study and 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.”

Noninvasive Techniques for Assessing Brain Circulation

The research team utilized two noninvasive techniques to study these changes:

• Transcranial Doppler ultrasound: This method tracks the speed of blood flow through the brain’s major arteries.
• Near-infrared spectroscopy: This technique evaluates how effectively oxygen reaches brain tissue near the surface of the cortex.

By combining these readings with advanced mathematical modeling, researchers created indicators of cerebrovascular function, reflecting the brain’s ability to adjust blood flow and oxygen delivery in response to natural fluctuations.

Study Findings: Vascular Health and Brain Changes

Participants with vascular indicators resembling those of cognitively healthy adults tended to have lower amyloid levels and a larger hippocampus. Conversely, individuals with mild cognitive impairment or dementia exhibited weaker vascular function. These findings reinforce the idea that declining blood vessel health in the brain is an integral part of the Alzheimer’s disease process.

“These vascular measures are capturing something meaningful about brain health,” said Meredith N. Braskie, PhD, senior author of the study and assistant professor of neurology at the Keck School of Medicine. “They appear to align with what we see on MRI and PET scans that are commonly used to study Alzheimer’s disease, providing important information about how vascular health and standard brain measures of Alzheimer’s disease risk may be related.”

Implications for Early Detection and Prevention

Arthur W. Toga, PhD, director of the Stevens INI, emphasized the significance of these findings: “These findings add to growing evidence that Alzheimer’s involves meaningful vascular contributions in addition to classic neurodegenerative changes. Understanding how blood flow and oxygen regulation interact with amyloid and brain structure opens new doors for early detection and potentially prevention.”

Compared to traditional methods like MRI and PET imaging, these noninvasive techniques are less costly, easier to administer, and do not involve radiation exposure or injections. This simplicity could facilitate large-scale screening and benefit individuals unable to undergo more intensive brain imaging.

Future Research and Ongoing Studies

Researchers caution that the current findings represent a snapshot in time and do not establish a direct cause-and-effect relationship. Ongoing longitudinal studies are tracking participants to determine if changes in vascular measures can predict future cognitive decline or response to treatment.

“If we can track these signals over time, we may be able to identify people at higher risk earlier and test whether improving vascular health can slow or reduce Alzheimer’s-related brain changes,” Tsiknia explained.

About the Study

The study was supported by the Office of The Director, National Institutes of Health, under Award Number S10OD032285, and by the National Institute on Aging [R01AG058162]. The research team included Peter S. Conti, Rebecca J. Lepping, Brendan J. Kelley, Rong Zhang, Sandra A. Billinger, Helena C. Chui, and Vasilis Z. Marmarelis, in addition to Tsiknia and Braskie.