Slight variations in a person’s pulse rate could give clues about the likelihood of future cognitive decline, according to a new study, potentially giving us a valuable new test for cognitive problems that would be quick and easy to run.
This is something that researchers invest a lot of time in, because knowing when cognitive decline might start, and how it may progress, means better support and more clarity for those involved. Along the way, it also reveals new insights into how these conditions develop, and how they might be stopped for good.
In this study, an international team analyzed pulse rate data across a night of sleep from 503 individuals with an average age of 82. Cognitive tests were also carried out around that same time, as well as in at least one follow-up visit.
Using a statistical model called distribution entropy that predicts health outcomes, the researchers found an association between pulse rate complexity – how much the pulse rate varied and adapted throughout the night – and cognitive decline in future years.
“Higher complexity of pulse rate is linked with slower cognitive decline in older adults,” write the researchers in their published paper. By contrast, reduced complexity was found to be associated with faster cognitive decline.
“Future studies should test whether complexity is also associated with future risks of neurodegenerative disorders, such as dementia, and further elucidate the causal directions.”
Distribution entropy is a relatively new, alternative method of measuring heart rate and the corresponding pulse rate sent through the body. Researchers have already linked this resting heartbeat complexity to other health risks, including cardiorespiratory problems.
The thinking is that a more adaptable heart is a healthier heart. If the heart is going through a more complex set of changes in response to what’s happening in the body, it’s operating in a more nimble and agile way, like a runner changing pace and direction.
Links have previously been suggested between heart rate variability and cognitive function, but this new type of measurement seems to go deeper, even predicting problems with brain health before noticeable symptoms appear.
“Heart rate complexity is a hallmark of healthy physiology,” says biomedical engineer and computational physiologist Peng Li, from Massachusetts General Hospital.
“Our hearts must balance between spontaneity and adaptability, incorporating internal needs and external stressors.”
More conventional measures of heart rate didn’t show any relationship to subsequent cognitive decline in this study, the researchers found, suggesting the distribution entropy approach might be more sensitive to health changes in the body.
Further research can now look at why this relationship exists, and the sort of biological pathways it’s operating along. The team also wants to analyze if there’s a relationship to the onset of dementia, as well as cognitive decline.
“The findings underscore the usefulness of our approach as a noninvasive measure for how flexible the heart is in responding to nervous system cues,” says Chenlu Gao, lead author and sleep scientist at Brigham and Women’s Hospital.
“It is suitable for future studies aimed at understanding the interplay between heart health and cognitive aging.”
The research has been published in the Journal of the American Heart Association.
