Your Brain's Blood Flow May Be the Hidden Key to Alzheimer's Risk—Here's Why Doctors Are Paying Attention

Researchers have discovered that small changes in how blood moves through your brain and delivers oxygen may be closely connected to Alzheimer's disease risk, potentially offering a new way to spot the disease before memory problems start. A new study from the Keck School of Medicine of USC found that people with healthier patterns of brain blood flow had lower levels of amyloid plaques—a hallmark of Alzheimer's—and larger hippocampi, the brain region critical for memory.

What Does Brain Blood Flow Have to Do With Alzheimer's?

For decades, scientists have focused on amyloid and tau proteins as the primary culprits in Alzheimer's disease. But this new research suggests the story is more complex. "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 a USC PhD candidate. When your brain's blood vessels don't function properly, they may struggle to deliver oxygen and nutrients to brain cells, potentially setting the stage for cognitive decline.

The study examined older adults both with and without cognitive impairment, measuring how well their brains regulated blood flow and oxygen levels. Participants whose vascular function resembled that of cognitively healthy adults tended to have lower amyloid burden and better-preserved memory centers in the brain.

How Are Researchers Measuring Brain Blood Flow?

The breakthrough here isn't just the discovery—it's the simplicity of the tools used to measure it. Researchers relied on two painless, noninvasive techniques that don't require injections, radiation, or demanding tasks:

• Transcranial Doppler Ultrasound: This technique tracks how quickly blood travels through the brain's major arteries, giving researchers a real-time picture of blood flow velocity.
• Near Infrared Spectroscopy: This method evaluates how effectively oxygen reaches brain tissue near the surface of the cortex, measuring oxygen saturation in the brain.
• Advanced Mathematical Modeling: Researchers combined these readings to create overall indicators of how well the brain adjusts blood flow and oxygen delivery in response to natural changes in blood pressure and carbon dioxide levels.

Unlike magnetic resonance imaging (MRI) and positron emission tomography (PET) scans—which are expensive, time-consuming, and sometimes require radioactive tracers—these vascular measures are simpler and more accessible.

Could This Lead to Earlier Detection of Alzheimer's?

The potential impact is significant. People diagnosed with mild cognitive impairment or dementia showed weaker vascular function compared to cognitively normal participants, suggesting that declining blood vessel health is part of the broader Alzheimer's disease progression. This opens the door to identifying people at risk before they experience noticeable memory loss.

"These vascular measures are capturing something meaningful about brain health," explained 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".

What's Next for Alzheimer's Prevention?

The researchers emphasize that this study represents a single snapshot in time and doesn't prove that poor blood flow causes Alzheimer's. However, ongoing long-term studies are tracking participants to see whether changes in vascular measures can predict future cognitive decline or response to treatment.

If future research confirms these findings, the implications could be transformative. "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 said. This could eventually lead to interventions focused on maintaining healthy brain blood vessels—potentially through exercise, cardiovascular health management, or other lifestyle factors—as a preventive strategy for Alzheimer's disease.

Arthur W. Toga, PhD, director of the Stevens Neuroimaging and Informatics Institute, noted that "understanding how blood flow and oxygen regulation interact with amyloid and brain structure opens new doors for early detection and potentially prevention". The simplicity and accessibility of these vascular measurement tools also make them promising candidates for large-scale screening programs, particularly for people who cannot undergo more intensive brain imaging.