Researchers have discovered that smartwatches can provide a more meaningful measure of cardiovascular health by calculating the ratio between heart rate and daily steps, according to findings presented at the American College of Cardiology meeting in Chicago.
The innovative metric, developed by researchers at Northwestern University Feinberg School of Medicine, measures how efficiently the heart responds to physical activity rather than just tracking activity levels alone. By dividing a person's average daily heart rate by their daily step count, the resulting ratio offers deeper insights into cardiovascular fitness.
"The metric we developed looks at how the heart responds to exercise, rather than exercise itself," explained lead researcher Zhanlin Chen, a medical student at Northwestern University. "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."
Comprehensive Data Analysis Reveals Strong Health Correlations
The research team analyzed data from nearly 7,000 American adults who provided Fitbit data and electronic health records to a National Institutes of Health research program. The dataset was substantial, encompassing 51 billion total steps and 5.8 million person-days of activity.
Results showed that people with a higher heart rate per step—indicating their hearts must work harder during physical activity—faced significantly elevated health risks:
- Twice the likelihood of having type 2 diabetes
- 1.7 times higher risk of heart failure
- 1.6 times greater chance of having hypertension
- 1.4 times increased risk of arterial blockages
Importantly, this new measure demonstrated stronger associations with cardiovascular disease diagnoses than either daily heart rate or step count alone. However, researchers noted no significant relationship between the metric and risk of stroke or heart attack.
Practical Applications for Patients and Healthcare Providers
The simplicity of this metric makes it particularly valuable, as people can calculate it themselves using data already collected by their smartwatches. Chen suggested the ratio could potentially be incorporated directly into smartwatch applications.
Healthcare providers could use this information to identify patients who might benefit from additional cardiovascular screening or targeted exercise interventions designed to improve heart function.
"Wearables are welcomed by the consumer and worn throughout the day, so they actually have minute-to-minute information about the heart function," Chen noted. "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."
The research team plans to investigate whether tracking heart rate per step across minutes rather than days would provide even more actionable information for clinical use.
Smartwatches Also Proving Valuable for Diabetes Management
In related research published in BMJ Open, smartwatches have demonstrated significant potential for helping people with type 2 diabetes establish and maintain exercise routines.
A study involving 135 newly diagnosed type 2 diabetes patients found that those provided with smartwatches paired with health apps were ten times more likely to begin an exercise program and three times more likely to still participate in that program a year later compared to those without such technology.
"The program offered a variety of workouts, including cardio and strength training, that could be done without the need for a gym," explained Katie Hesketh, assistant professor in exercise prescription at the University of Birmingham. "Its goal is to make exercise a sustainable part of daily life for people with type 2 diabetes, ultimately improving their physical and mental health."
The smartwatch-guided program gradually increased participants' physical activity to a target of 150 minutes per week of moderate to vigorous exercise. Participants also received support from exercise specialists through an online coaching service.
Early results indicated improvements in blood sugar control and blood pressure among participants, though researchers plan to conduct larger clinical trials to confirm these benefits.
"We found that using biometrics from wearable technologies offered great promise for encouraging people with newly diagnosed type 2 diabetes to maintain a home-delivered, personalized exercise program with all the associated health benefits," Hesketh concluded.
The Future of Wearable Health Technology
As wearable technology continues to evolve, these studies highlight the growing potential for smartwatches to move beyond simple activity tracking to provide more sophisticated health insights and interventions.
The heart rate-to-step ratio represents a significant advancement in how consumer technology can be leveraged to assess cardiovascular health, while guided exercise programs demonstrate how these devices can facilitate behavioral changes that improve health outcomes.
Health economists see broad implications for these technologies. "The results of these studies can contribute to change the lives of many people around the world," noted Ceu Mateus, professor of health economics at Lancaster University. "There are millions of people suffering from diabetes type 2 without access to non-pharmacological interventions with sustained results in the long term."
As researchers continue to explore new applications for wearable technology data, smartwatches may increasingly serve as valuable tools for both preventive healthcare and chronic disease management.
