Beware: Fluctuating Blood Pressure May Harm The Brain, Study Warns

Even if your blood pressure readings appear normal, frequent fluctuations from one heartbeat to the next could put your brain at risk. Older adults whose blood pressure varies significantly over short periods may face a higher likelihood of brain shrinkage and nerve cell injury, according to a new study.

Led by the USC Leonard Davis School of Gerontology, the research — published in the Journal of Alzheimer’s Disease on October 17 — found that short-term “dynamic instability” in blood pressure, or rapid moment-to-moment changes measured over minutes, is linked to loss of brain tissue in regions critical for memory and cognition. The study also identified elevated levels of blood biomarkers indicating nerve cell damage among those with greater fluctuations.

“Our findings show that even when average blood pressure is normal, fluctuations from one heartbeat to the next may place stress on the brain,” said Daniel Nation, Professor of Gerontology and Medicine at USC Leonard Davis School and senior author of the study. “These moment-to-moment swings appear to be associated with the same types of brain changes seen in early neurodegeneration.”

While sustained high blood pressure is a well-established risk factor for dementia, this research focuses on blood pressure variability — how much blood pressure rises and falls over short intervals. Emerging evidence indicates that such fluctuations may strain small cerebral vessels, impairing their ability to maintain steady blood flow.

In the study, researchers assessed two key indicators: Average Real Variability (ARV), which captures how much systolic blood pressure changes between heartbeats, and the Arterial Stiffness Index (ASI), which measures how flexible the arteries are in response to those changes. Together, they reflect the degree of “blood pressure dynamic instability.”

“Blood pressure is not static; it constantly adapts to the body’s needs,” Nation explained. “But as we age, that regulation becomes less precise. Excessive fluctuations may therefore reflect vascular ageing that contributes to brain injury.”

The study involved 105 healthy older adults, aged 55 to 89, with no major neurological disorders. During MRI scans, participants’ blood pressure was continuously monitored using a finger-cuff device that recorded each beat over a seven-minute period. The researchers then analysed how these fine-scale fluctuations corresponded with brain structure and blood biomarkers linked to neurodegeneration.

MRI scans showed that participants with both high ARV and high ASI — indicating unstable blood pressure and stiff arteries — had smaller hippocampal and entorhinal cortex volumes, areas critical for learning and memory and among the first affected in Alzheimer’s disease. Blood tests revealed higher levels of neurofilament light (NfL), a biomarker that increases when nerve cells are damaged.

These associations held even after adjusting for age, sex, and average blood pressure, suggesting that fluctuations themselves, not overall levels, may contribute to brain decline. Notably, the changes were more pronounced on the left side of the brain, consistent with earlier studies suggesting that the left hemisphere is more vulnerable to vascular stress and neurodegenerative conditions.

The findings offer new insights into how cardiovascular instability may accelerate cognitive decline and open potential avenues for prevention.

“Traditionally, clinical focus has been on lowering average blood pressure,” said Trevor Lohman, USC Research Assistant Professor of Neurology and Gerontology and the study’s first author. “Our results suggest that maintaining stable blood pressure could be just as important for protecting brain health — even when average readings appear normal.”

“Our results underscore the deep connection between heart health and brain health,” Lohman added. “Maintaining steady, healthy blood flow may be one of the most effective ways to preserve cognitive function with age.”

The study was conducted by researchers from USC, UC Irvine, and UCSF, with support from the US National Institutes of Health, the American Heart Association, and the Southern California Clinical and Translational Science Institute.