A healthy heart is not only defined by its strength or regularity, but also by its capacity to adapt. This adaptability manifests in the subtle complexity of each heartbeat, which responds dynamically to internal physiological demands and shifts in the external environment. Researchers at Mass General Brigham have introduced a novel technique for measuring this complexity in pulse rates, using data collected through wearable pulse oximetry technology. Their innovative method, detailed in the Journal of the American Heart Association, offers a more nuanced view of cardiac health than traditional heart rate variability metrics. Intriguingly, the study also establishes a connection between reduced pulse rate complexity and an increased risk of cognitive decline in older adults.
“Heart rate complexity is a hallmark of healthy physiology,” explained Dr Peng Li, senior author of the study and a researcher in the Department of Anaesthesia, Critical Care and Pain Medicine at Massachusetts General Hospital (MGH). He also holds a position in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital (BWH), both founding institutions of the Mass General Brigham healthcare network. “Our hearts must maintain a delicate balance between responsiveness and stability, dynamically adjusting to both internal signals and external stressors,” underscoring the physiological significance of heartbeat complexity as a biomarker for overall health.
The researchers employed data from 503 elderly participants (average age 82, 76% of whom were women) enrolled in the Rush Memory and Aging Project, a long-standing and well-regarded cohort study. They analysed pulse rate data recorded overnight using the Itamar WatchPAT 300—a fingertip-worn oximetry device—alongside comprehensive cognitive assessments conducted contemporaneously and during follow-up visits up to 4.5 years. This longitudinal design allowed the researchers to track cognitive trajectories regarding baseline heart function over time.
Their findings were striking. Participants who exhibited greater baseline complexity in their pulse rates tended to experience slower cognitive decline over the ensuing years. This relationship held even when conventional markers of heart rate variability failed to predict similar outcomes, suggesting that the newly developed metric is more sensitive in capturing aspects of cardiac function relevant to brain health. These results indicate a potential shift in how cardiovascular indicators assess neurological risk, particularly in ageing populations.
Looking ahead, the research team intends to investigate whether this pulse rate complexity measure can be an early predictor of dementia. Should such a link be confirmed, the technique could prove invaluable in identifying individuals at heightened risk during preclinical stages of cognitive impairment, when therapeutic intervention might be most effective. This could represent a significant advance in preventive strategies aimed at delaying or mitigating the progression of neurodegenerative conditions such as Alzheimer’s disease.
“Our findings highlight the value of this new approach as a non-invasive indicator of how flexibly the heart responds to input from the nervous system,” said Dr Chenlu Gao, lead author of the study and fellow researcher at MGH. “Its utility extends beyond mere cardiac assessment—it opens a window into understanding the complex interplay between heart health and cognitive ageing.” The development of such metrics could pave the way for a more integrated view of physiological wellbeing in later life, recognising the interdependence of cardiovascular and neurological systems in maintaining quality of life across the ageing process.
More information: Chenlu Gao et al, Reduced Complexity of Pulse Rate Is Associated With Faster Cognitive Decline in Older Adults, Journal of the American Heart Association. DOI: 10.1161/JAHA.125.041448
Journal information: Journal of the American Heart Association Provided by Mass General Brigham
