Researchers from Brigham and Women’s Hospital, part of the Mass General Brigham healthcare system, have developed a novel approach to evaluating heart rate that may offer valuable insights into future cognitive health. Published in the Journal of the American Heart Association, this study highlights a more sensitive method for assessing cardiovascular function using wearable pulse oximeters. The findings suggest that a loss of complexity in heart rate patterns may be a warning sign of faster cognitive decline in older adults.
A healthy heart is highly adaptive. Its rhythm shifts in response to both internal demands and external environments, showing intricate patterns that reflect a balanced physiological system. Dr. Peng Li, senior author and a researcher in anesthesiology, critical care, and pain medicine at Massachusetts General Hospital, as well as a specialist in sleep and circadian disorders at Brigham and Women’s Hospital, explained that this complexity represents a hallmark of physiological resilience. “The heart needs to strike a balance between spontaneity and adaptability,” Dr. Li said. “It must respond to both internal signals and external challenges.”
To test this theory, researchers analyzed data from 503 participants in the Rush Memory and Aging Project, an ongoing study involving older adults in the United States. The average age of participants was 82 years, and 76% were women. Each participant wore a fingertip pulse oximeter device (the Itamar WatchPAT 300) during sleep, which recorded their heart rate variability throughout the night. At the same time, cognitive function was assessed using standardized tests. These assessments were repeated annually for an average of 4.5 years.
The key innovation of this study lies in how the researchers measured the heart’s beat-to-beat variability. Rather than using conventional heart rate variability (HRV) analysis, they applied a technique that captures the complexity of the heart rate signals. This complexity refers to how rich and unpredictable the heart’s rhythm is—something not adequately represented by traditional HRV metrics.
What the researchers found was striking: participants whose heart rate complexity was higher at the start of the study experienced significantly slower rates of cognitive decline over time. This association held even after adjusting for common confounding variables such as age, sex, education level, and baseline cognitive function. Furthermore, traditional HRV measures did not predict cognitive decline, suggesting that the new method captures something fundamentally different—and more predictive—about cardiovascular health.
Lead author Dr. Chenlu Gao from Massachusetts General Hospital emphasized the significance of these findings. “Our method provides a noninvasive way to evaluate how flexibly the heart responds to nervous system inputs,” she said. “It offers a new tool to understand the interplay between cardiac function and brain aging.”
The implications of this research could be profound. If heart rate complexity proves to be a reliable early marker for cognitive decline, it could enable physicians to identify at-risk individuals long before symptoms of dementia or other neurodegenerative diseases appear. Interventions—whether lifestyle modifications, medications, or other therapies—could be introduced earlier, potentially delaying or mitigating cognitive deterioration.
The study’s authors now plan to investigate whether reduced heart rate complexity can predict the onset of dementia itself, not just general cognitive decline. If so, wearable pulse oximeters could become essential tools in geriatric care, offering a simple, at-home way to monitor brain health via the heart.
In a broader sense, the research adds to the growing body of evidence that cardiovascular and neurological health are deeply interconnected. The heart and brain communicate through complex neural and biochemical pathways, and disruptions in one system often echo in the other. Understanding this dialogue could unlock new strategies for preventing age-related diseases.
As the aging population continues to grow, finding accessible, accurate, and cost-effective ways to track cognitive health is increasingly urgent. The use of wearable technology—already common in consumer fitness and wellness products—could be adapted for clinical purposes with relatively low barriers. This study provides a promising step in that direction.
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