Even if your blood pressure numbers look good, wide swings from one heartbeat to the next could spell trouble for your brain, according to new research from the University of Southern California.
The study, published in the Journal of Alzheimer’s Disease, found that short-term “dynamic instability” in blood pressure—rapid changes happening over the course of mere minutes—is linked to brain shrinkage in areas crucial for memory and thinking, as well as to blood markers that indicate nerve cell damage.
“Our findings show that even when average blood pressure is normal, instability from one heartbeat to the next may place stress on the brain,” said paper author and gerontologist professor Daniel Nation in a statement. “These moment-to-moment swings appear to be associated with the same kinds of brain changes we see in early neurodegeneration.”
Why Blood Pressure Stability Matters
High blood pressure has long been associated with an increased dementia risk, but this study looked at something different—by how much blood pressure fluctuates over short periods of time. Sudden ups and downs can strain tiny blood vessels in the brain, making it harder for them to deliver steady oxygen and nutrients.
Researchers focused on two key measures:
- Average Real Variability (ARV): how much systolic blood pressure (the top number) changes between each heartbeat.
- Arterial Stiffness Index (ASI): how flexible or stiff the arteries are as they respond to those changes.
Together, these show how stable—or unstable—someone’s blood flow is, a concept the team calls “blood pressure dynamic instability.”
“Blood pressure isn’t static; it’s always adapting to the body’s needs,” explained Nation. “But as we age, that regulation can become less precise. This study suggests that excessive fluctuations could be a sign of vascular aging that contributes to brain injury.”
What the Researchers Did
The research involved 105 older adults, aged 55–89, who were generally healthy and had no major neurological conditions. During MRI scans, participants wore a finger cuff that continuously tracked blood pressure for seven minutes, capturing every single heartbeat.
Those with both a high ARV and high ASI—meaning that they had unstable pressure and stiff arteries—showed smaller volumes in the hippocampus and entorhinal cortex, two brain regions essential for learning and memory and among the first to deteriorate in Alzheimer’s disease.
Blood tests revealed that these same participants also had higher levels of neurofilament light (NfL), a protein released into the blood when nerve cells are damaged.
Importantly, these links remained strong even after accounting for age, sex and overall blood pressure levels. That means that is may be that the fluctuations themselves, not just high pressure, also pose a threat.
Interestingly, the changes appeared more severe on the left side of the brain—a pattern seen in past studies suggesting the left hemisphere may be more vulnerable to stress from unstable blood flow.
What This Means for Preventing Dementia
According to the researchers, these findings could change how doctors think about managing heart health to protect the brain.
“Traditionally, we’ve focused on lowering average blood pressure numbers,” said paper author and gerontologist professor Trevor Lohman.
“But this study suggests we should also be looking at how stable blood pressure is from moment to moment. Reducing these fluctuations could help protect the brain, even in people whose average readings look fine.”
Future studies will look at whether stabilizing blood pressure—through adjusting medication timing, regular exercise or stress management—could slow brain aging and reduce dementia risk.
Because this study was cross-sectional, it shows a link but not proof of cause and effect, so further, long-term research will be needed.
“Our results underscore how closely connected the heart and brain are,” Lohman added. “Maintaining steady, healthy blood flow could be one of the best ways to support brain health as we age.”
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Reference
Lohman, T., Shenasa, F., Sible, I., Kapoor, A., Engstrom, A. C., Dutt, S., Head, E., Sordo, L., Alitin, J. P. M., Gaubert, A., Nguyen, A., Pahlevan, N., & Nation, D. A. (2025). Blood pressure dynamic instability and neurodegeneration in older adults. Journal of Alzheimer’s Disease. https://doi.org/10.1177/13872877251386443
