We often think of high blood pressure as the main heart-related risk to our brain health.
But new research shows that even when average blood pressure is under control, rapid ups and downs from one heartbeat to the next could still quietly damage the brain.
The study, led by researchers at the USC Leonard Davis School of Gerontology, sheds light on a less familiar problem: blood pressure instability.
Published in the Journal of Alzheimer’s Disease, the study focused on how short-term, moment-to-moment changes in blood pressure—called “dynamic instability”—can affect brain size and health.
These tiny swings in pressure, measured over just a few minutes, were linked to brain shrinkage in areas that control memory and thinking, and to blood signs of nerve cell damage.
Lead researcher Dr. Daniel Nation explained, “Even if your average blood pressure looks normal, having sudden spikes and drops from one beat to the next can still stress the brain. We’re seeing the same types of changes in the brain that happen early in diseases like Alzheimer’s.”
Scientists have known for a long time that high blood pressure over time increases the risk for dementia. But this study went beyond the average numbers. It looked at how much a person’s blood pressure goes up and down in a short time.
This kind of instability may strain the small blood vessels in the brain and affect steady blood flow, which is essential for healthy brain function.
To measure these rapid changes, the team used two tools: one called Average Real Variability (ARV), which shows how much systolic pressure (the top number in a blood pressure reading) changes between each heartbeat, and another called the Arterial Stiffness Index (ASI), which measures how flexible or stiff the blood vessels are.
Together, these tell researchers how unstable a person’s blood pressure is and how well their arteries can respond.
The study involved 105 older adults between the ages of 55 and 89, all generally healthy with no major brain disorders. While participants were in an MRI machine, their blood pressure was recorded beat by beat using a finger sensor for seven minutes.
The scans showed that people with more unstable blood pressure and stiffer arteries had smaller brain areas related to memory and learning—specifically, the hippocampus and entorhinal cortex. These are the same areas that shrink in the early stages of Alzheimer’s disease.
The blood samples told a similar story. Participants with high ARV and ASI had higher levels of a protein called neurofilament light (NfL), which appears in the blood when nerve cells are damaged.
These findings remained important even after researchers adjusted for age, sex, and average blood pressure, meaning that the moment-to-moment pressure changes were independently linked to brain injury.
Interestingly, the damage seemed worse in the left side of the brain. This supports other studies suggesting that the left side may be more vulnerable to stress and age-related decline. Scientists think this could be due to differences in how the two sides of the brain receive blood or manage blood flow.
These findings offer new ideas for preventing dementia. Until now, most efforts have focused on keeping average blood pressure low. But this study suggests it may also be important to keep blood pressure stable from moment to moment.
Dr. Trevor Lohman, the study’s first author, says that finding ways to smooth out these swings—perhaps through better medication timing, exercise, or stress management—might protect the brain, even in people whose average blood pressure looks fine.
While the study doesn’t prove that unstable blood pressure causes brain shrinkage—it was a snapshot in time—it does show a strong link. More long-term research is needed to confirm the findings and test whether stabilizing blood pressure can slow brain aging.
Still, the message is clear: your heart and brain are closely connected. Keeping your blood flowing smoothly may be just as important as keeping your pressure low. As we age, paying attention to the rhythm of that flow could help preserve memory, thinking, and overall brain health.
If you care about Alzheimer’s disease, please read studies about Research shows root cause of Alzheimer’s disease and new treatment and findings of Scientists find the link between eye disease glaucoma and Alzheimer’s disease.
If you care about Alzheimer’s disease, please read studies about Scientists find a new way to treat Alzheimer’s disease and findings of Fluctuating cholesterol and triglyceride levels are linked to Alzheimer’s disease.
The study is published in the Journal of Alzheimer’s Disease.
Copyright © 2025 Knowridge Science Report. All rights reserved.
