Even when overall blood pressure falls within a healthy range, older adults whose readings fluctuate sharply from one heartbeat to the next may still face a greater risk of brain shrinkage and nerve cell injury. New research from the USC Leonard Davis School of Gerontology suggests that blood pressure instability, rather than high averages alone, can harm the brain and may signal early signs of neurodegeneration. The findings expand the understanding of cardiovascular risk by showing that the moment-to-moment consistency of blood pressure matters as much as long-term control.
Published online on 17 October in the Journal of Alzheimer’s Disease, the study examined a form of short-term variation known as “dynamic instability,” referring to fluctuations occurring over just minutes. Researchers found that these rapid shifts are associated with reduced volume in brain regions responsible for memory and cognition, as well as with blood markers indicating nerve cell damage. According to senior author Daniel Nation, even routine blood pressure readings may mask subtle instability that can place the brain under stress. He notes that such instability appears linked to the same kinds of changes observed early in neurodegenerative conditions such as Alzheimer’s disease.
While high average blood pressure has long been recognised as a significant risk factor for dementia, the study highlights the importance of blood pressure stability. Frequent small rises and falls may strain tiny blood vessels that supply the brain, reducing their ability to maintain steady blood flow. Over time, this stress may weaken neural tissue, suggesting that maintaining stable circulation could be key to protecting cognitive function.
To measure instability, the research team used two indicators. The first, Average Real Variability (ARV), measures the extent to which systolic blood pressure shifts between heartbeats. The second, the Arterial Stiffness Index (ASI), reflects how flexible the artery walls are as they respond to changing pressure. Together, these metrics offer a picture of how blood flow fluctuates over short periods and indicate “blood pressure dynamic instability.” Nation explains that although the cardiovascular system constantly adapts to the body’s needs, this regulation may become less precise with age, resulting in exaggerated swings that burden the brain.
The study involved 105 adults aged 55-89 with no significant neurological disease. During MRI scans, each participant’s blood pressure was recorded beat-by-beat for 7 minutes. Researchers examined how these fluctuations related to brain structure and blood biomarkers associated with neurodegeneration. Individuals with both high ARV and high ASI showed smaller volumes in the hippocampus and entorhinal cortex, regions vital for memory and among the first affected in Alzheimer’s disease. Blood samples from these individuals also revealed higher levels of neurofilament light (NfL), a marker of nerve cell damage. Notably, the associations held even after accounting for age, sex, and average blood pressure, indicating that variability itself may be an independent risk factor.
Lead author Trevor Lohman suggests that focusing solely on lowering average blood pressure may not be enough. Approaches that reduce fluctuations—through exercise, tailored medication timing, or stress reduction—may offer additional protection. Although the study cannot prove causation, it points to new ways to prevent dementia by maintaining steady blood flow. As the link between cardiovascular stability and brain health becomes clearer, protecting the brain may rely not only on lowering blood pressure but on keeping it consistently stable as we age.
More information: Daniel Nation et al, Blood pressure dynamic instability and neurodegeneration in older adults, Journal of Alzheimer’s Disease. DOI: 10.1177/13872877251386443
Journal information: Journal of Alzheimer’s Disease Provided by University of Southern California
