Scientists Just Discovered a Smartwatch Formula That Could Change How We Detect Heart Disease

A new study suggests your smartwatch could provide a powerful insight into your heart health.

Researchers developed a metric called Daily Heart Rate Per Step (DHRPS), which outperforms traditional measures like step count or heart rate in predicting cardiovascular risk. Those with high DHRPS were significantly more likely to suffer from serious heart-related conditions, suggesting this simple calculation could help detect early warning signs of disease.

Smartwatches and Heart Health: A New Breakthrough

Your smartwatch might hold valuable insights into your heart health, according to new research. Scientists have developed a method to assess cardiovascular fitness using data routinely collected by smartwatches. The findings will be presented at the American College of Cardiology’s Annual Scientific Session (ACC.25).

The study suggests that dividing a person’s average daily heart rate by their daily step count provides a more reliable measure of cardiovascular fitness than looking at heart rate or step count alone.

Why This Metric Matters More Than Just Steps or Heart Rate

“The metric we developed looks at how the heart responds to exercise, rather than exercise itself,” said Zhanlin Chen, a medical student at Northwestern University Feinberg School of Medicine in Chicago and the study’s lead author. “It’s a more meaningful metric because it gets at the core issue of capturing the heart’s capacity to adjust under stress as physical activity fluctuates throughout the day. Our metric is a first attempt at capturing that with a wearable device.”

Heart disease remains the leading cause of death in the United States. While existing screening tests can detect early warning signs, many people do not undergo these evaluations. Researchers believe smartwatch data could help bridge this gap by identifying individuals at higher risk and encouraging them to seek medical advice about their heart health.

A Massive Study With Billions of Steps Analyzed

For the study, researchers analyzed data from nearly 7,000 U.S. adults who provided data from their Fitbit and electronic health records to the All of Us research program, a nationwide prospective study supported by the National Institutes of Health. Together, the data reflected 5.8 million person-days and 51 billion total steps taken.

Calculating the relationship between participants’ average daily heart rate per step (DHRPS) and a variety of cardiovascular outcomes, data showed that people with elevated DHRPS (in the top 25^th percentile) 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 people who had lower DHRPS. No relationship was found between DHRPS and the risk of a stroke or heart attack.

A Stronger Predictor Than Traditional Metrics

The results also showed that DHRPS was more strongly associated with cardiovascular disease diagnoses than either daily heart rate or step count alone. Additionally, in a smaller subset of 21 participants, DHRPS was more strongly linked to maximum metabolic equivalents (METs) achieved on a treadmill stress test than either daily heart rate or step count alone.

Based on the findings, the researchers suggest that DHRPS could be used as an early indicator of who might benefit from more screening tests or cardiovascular conditioning to improve their heart’s functioning. According to Chen, the metric is simple enough that an individual could calculate it on their own based on the data collected by a smartwatch, or it could potentially be built into smartwatch applications.

Next Steps: Refining the Science Behind DHRPS

However, he added that the study offers only an initial validation of the DHRPS approach, and the cross-sectional study design did not allow researchers to determine when the Fitbit measurements were taken relative to when cardiovascular disease outcomes were diagnosed. Moving forward, the researchers hope to conduct more prospective studies with a higher temporal resolution, tracking DHRPS at the scale of minutes rather than aggregated data across days.

With further refinement and validation, Chen said that DHRPS or a similar metric could ultimately be incorporated into the standard heart disease risk assessment that clinicians use.

Unlocking the Full Potential of Wearable Technology

“Wearables are welcomed by the consumer and worn throughout the day, so they actually have minute-to-minute information about the heart function,” Chen said. “That is a lot of information that can tell us about a lot of things, and there’s a need to further study how this detailed information correlates with patient outcomes.”

Chen will present the study, “Daily Heart Rate Per Step (DHRPS) as a New Wearables Metric Associated with Cardiovascular Disease,” on Saturday, March 29, 2025, at 9:30 a.m. CT / 14:30 UTC in Moderated Poster Theater 10.

ACC.25 will take place March 29-31, 2025, in Chicago, bringing together cardiologists and cardiovascular specialists from around the world to share the newest discoveries in treatment and prevention.

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