That most smartwatches and fitness bands allow you to monitor your heart rate is not news. That it allows you to detect diseases earlier (yourself) is also known. However, that there is also a very easy way to use a smartwatch to assess the condition of your heart is certainly one. It seems unlikely, but an international study has shown that it is indeed possible. All you need for it is the average measured heart rate and number of steps for a given day.
The research, to be presented at the American College of Cardiology's Annual Scientific Session (ACC.25) in late March, discusses a method by which heart health can be assessed by dividing the average heart rate on a day, measured by a smartwatch for example, by the total number of steps taken that same day.
Average heart rate divided by number of steps
The method developed by the researchers appears to be -compared to assessing only heart rate or only number of steps- a more reliable indicator of a person's cardiovascular fitness. “The metric we developed looks at how the heart responds to exertion, rather than the exertion itself. And that's exactly what it's about: the heart's ability to adapt under stress as physical activity fluctuates throughout the day,” said Zhanlin Chen, a medical student at Northwestern University Feinberg School of Medicine in Chicago.
About the study
For the study, data from nearly 7,000 American adults were analyzed. These were all people who provided data from their Fitbit and electronic health records to the All of Us research program. Collectively, the data represented heart rate data for 5.8 million days and 51 billion steps.
By calculating the relationship between the average daily heart rate per step (DHRPS) per participant and various cardiovascular outcomes, the data showed that people with an elevated DHRPS (in the top quarter of the measurements) were about twice as likely to have type 2 diabetes, 1.7 times as likely to have heart failure, 1.6 times as likely to have high blood pressure and 1.4 times as likely to have coronary atherosclerosis (a buildup of plaque in the heart's arteries), compared with those with a lower DHRPS. No association was found between DHRPS and the risk of stroke or heart attack.
The results also showed that DHRPS was more strongly associated with diagnoses of cardiovascular disease than daily heart rate or number of steps alone. Moreover, in a smaller subgroup of 21 participants, DHRPS was more strongly associated with maximum metabolic equivalents (METs) obtained during a treadmill stress test than daily heart rate or number of steps alone.
Early indicator
The researchers now argue that their findings show that DHRPS can be used as an early indicator of who might benefit from more screening tests or cardiovascular conditioning to improve their heart functioning. In addition, researcher Chen states that the metrics are simple enough to be calculated by users themselves or integrated into an app.
In doing so, he does note that the study offers only an initial validation of the DHRPS approach and that the cross-sectional study design did not allow the researchers to determine when Fitbit measurements were taken versus when cardiovascular disease outcomes were diagnosed. The researchers hope to conduct more prospective studies in the future with higher temporal resolution, tracking DHRPS on the scale of minutes rather than aggregated data over days.
