Many people use smartwatches to monitor cardiovascular health. Often, they count the steps they take over during the day, or record the average daily heart rate. Currently, researchers are proposing enhanced metrics that combine the two using basic mathematics. Divide the average daily heart rate by the average daily steps.
According to a study conducted by researchers at the Feinberg Medicine of Medicine at Northwestern University and published today in the Journal of the American Heart Association, the results ratio – daily heart rate per step, or DHRP, provides insight into how efficiently the heart is functioning.
This study found that people with reduced cardiac efficiency are more likely to experience a variety of diseases, including type II diabetes, hypertension, heart failure, stroke, coronary atherosclerosis, and myocardial infarction.
“This is a measure of inefficiency,” said Zhanlin Chen, a third-year medical student at the Feinberg School of Medicine at Northwestern University and a lead author of the new study. His co-authors included several Feinberg faculty doctors. “It sees how badly your mind is doing,” he added. “I just have to do a little bit of math.”
Some experts said they saw DHRP wisdom as an indicator. Dr. Peter Aziz, a pediatric cardiologist at Cleveland Clinic, said that daily steps or average heart rate is an advancement in information provided.
“Argh, perhaps more important for aerobic exercise, is to hold your heart with the amount of work your mind has to do,” he said. “This is a reasonable way to measure it.”
The metric does not look at your heart rate while exercising. However, Dr. Aziz said it still provides a sense of overall efficiency and, importantly, it has been shown by researchers to be linked to the disease.
The size of the study added validity to the findings, Dr. Aziz said. Scientists mapped FITBIT data from around 7,000 smartwatch users to electronic medical records.
Chen said an easy way to grasp the value of the new metric is to compare two virtual individuals. Both have 10,000 steps per day, with one in the middle of the healthy range and an average daily resting heart rate of 80, while the other daily resting heart rate is 120.
The first person has a DHRPS of 0.008 and a second 0.012. The higher the proportion, the stronger the signaling of cardiac risk.
In this study, 6,947 participants were divided into three groups based on ratio. The best people showed a stronger association with illness than other participants. DHRPS metrics were also better at identifying disease risk than just graded numbers and heart rate, research found.
“The metric was designed to be low-cost and to use the data we already collect,” Chen said. “People who want to take charge of their health can do a little math to understand this.”
