Alzheimer's Disease May Begin with Subtle Decline in Brain Blood Flow: Study Shows

Subtle changes in how blood flows through the brain and how oxygen is delivered to brain cells may be closely tied to the risk of Alzheimer's disease, according to new research from the Mark and Mary Stevens Neuroimaging and Informatics Institute at the Keck School of Medicine of USC.

The study, published in Alzheimer's & Dementia, examined older adults with and without cognitive impairment and found that simple, noninvasive measures of brain circulation were linked to key markers of Alzheimer’s, including amyloid plaque buildup and shrinkage of the hippocampus, a region critical for memory.

Researchers used amyloid PET imaging to measure plaque accumulation in the brain, where warmer colors indicate higher amyloid levels. Participants whose brain blood flow and oxygen regulation patterns more closely resembled those seen in healthy aging tended to have lower amyloid burden and larger hippocampal volumes.

These features are associated with reduced Alzheimer’s risk, reinforcing the idea that vascular health may influence early disease-related changes.

To assess cerebrovascular function, the team used transcranial Doppler ultrasound to track blood flow speed in major brain arteries and near-infrared spectroscopy to evaluate oxygen delivery to cortical tissue.

Advanced mathematical modeling combined these readings into overall indicators reflecting how well the brain adjusts blood flow and oxygen in response to natural fluctuations in blood pressure and carbon dioxide.

Individuals with mild cognitive impairment or dementia showed weaker vascular function compared to cognitively normal participants.

Although the findings do not prove cause and effect, they suggest that monitoring brain vascular health could support earlier, more accessible screening and potentially guide prevention strategies in Alzheimer’s disease.

REFERENCE: Amaryllis A. Tsiknia, Jamie A. Terner, Zoe E. Tsokolas, Dae C. Shin, Elizabeth B. Joe, Peter S. Conti, Rebecca J. Lepping, Brendan J. Kelley, Rong Zhang, Sandra A. Billinger, Helena C. Chui, Vasilis Z. Marmarelis, Meredith N. Braskie. Cerebrovascular regulation dynamics and Alzheimer\'s neuroimaging phenotypes. Alzheimer\'s, 2026; 22 (2) DOI: 10.1002/alz.71146