The line between wearable activity trackers and clinical-grade health monitors seems to be getting blurrier by the day. A new study from researchers at Johns Hopkins University shows that consumer activity-tracking wearables may support clinical care. The study’s first author Zheng “Peter” Xu says, “The purpose of this study was to show that clinically relevant metrics beyond daily step count can be derived from these wearable activity monitors…. Historically, remote monitoring of a patient’s physical status has been challenging. We wanted to meet that challenge and see what kind of untapped information is contained within these devices that could help us support patients with [pulmonary arterial hypertension (PAH)].”

To gauge the use of information collected by activity trackers, Xu and his team took data from 22 people with PAH who wore Fitbits between two visits to the Cleveland Clinic. During the clinic visits, the study’s participants engaged in physical activity and medical professionals took 26 health measurements. These metrics included those for cardiopulmonary functions derived from the standard six-minute walk test that’s commonly used in the care of patients with cardiac and respiratory diseases. Researchers then compared the clinical data they collected to Fitbit heart rate and minute-to-minute step-rate data — finding some correlations they didn’t expect.  

An example of one such correlation: an activity tracker’s fitness assessment, based on heart rate data and step count information, was in line with clinically measured levels of N-terminal pro b-type natriuretic peptides (NT-proBNPs). This blood biomarker can serve as a red flag for the risk of congestive heart failure, as a high level of NT-proBNP often means that a person’s body needs more blood than the heart is pumping. The study’s senior author Peter Searson says, “[This] suggests to us that activity-tracker data may make it possible to identify surrogate markers of disease severity that can be monitored remotely. These data could potentially contribute to the identification of patients who would benefit from more frequent clinic visits or specific medications.” 

The study posits, “These results highlight the fact that daily step count is only one of many metrics that can be derived from activity monitors.” And so the research team is continuing with an exploration into how activity trackers could be used in conjunction with clinical care for people with the skin disease scleroderma and chronic obstructive pulmonary disease (COPD), working with the Johns Hopkins COPD Precision Medicine Center of Excellence to see how fitness-focused wearables can forecast the probability of COPD flareup.