Alzheimer's disease is diagnosed by its end products: amyloid plaques, tau tangles, hippocampal atrophy, cognitive decline. By the time these are detectable, the disease has been progressing for years, possibly decades. Published in Alzheimer's and Dementia in February 2026, researchers at USC's Stevens INI demonstrated that subtle changes in brain blood flow and oxygen utilization are correlated with amyloid burden and hippocampal volume — the two hallmarks of Alzheimer's risk — in cognitively healthy adults.
The measurement technique is notable for what it avoids. Transcranial Doppler ultrasound measures blood velocity through major brain arteries. Near-infrared spectroscopy measures cortical oxygenation. Neither requires MRI, PET scans, radioactive tracers, injections, or active participation from the patient. The data enters a mathematical model that summarizes how well the brain adjusts blood flow and oxygen delivery in response to natural variations in blood pressure and carbon dioxide levels. The output is a vascular health indicator — not a disease marker, but a plumbing report.
The structural insight is about early signals hiding in infrastructure. Alzheimer's research has focused on the pathological endpoints — the plaques, the tangles, the atrophy. The USC result suggests that the disease process may begin with the vascular system that serves the brain, not the neurons themselves. The brain's blood supply degrades subtly, oxygen delivery becomes less responsive, and the resulting metabolic stress creates conditions that favor amyloid accumulation. The plaque is a symptom of the supply failure, not the other way around.
This inverts the therapeutic target. If amyloid accumulation is downstream of vascular dysfunction, then clearing amyloid (the approach of most current drugs) treats the consequence. Maintaining vascular health — cheap, low-tech, measurable with ultrasound — treats the cause. The most important Alzheimer's diagnostic might not be a brain scan. It might be a blood flow measurement that costs a fraction as much and can be repeated indefinitely.