Your smartwatch is smarter than you think, study finds — it can predict blood tests

A study led by Stanford University School of Medicine researchers shows commercial smartwatches can predict simple blood test results by flagging early signs of dehydration, anemia or illness with measurements typically revealed during clinical visits. (AP photo)

Rings, watches and bracelets are no longer just fashion statements; they’re highly complex technologies that can monitor what’s going on inside your body in real time.

Now, a study led by Stanford University School of Medicine researchers shows commercial smartwatches can predict simple blood test results by flagging early signs of dehydration, anemia or illness with measurements typically revealed during clinical visits.

In some cases, smartwatches were able to give more consistent and precise vital signs than those taken at doctor’s offices, according to the study published Monday in the journal Nature Medicine, which is “among the first” to show how smartwatch data matches up with laboratory tests.

Although smartwatches should not replace doctors, the researchers say measurements of heart rate, body temperature, physical activity and oxygen levels taken over prolonged periods can help assess overall health or even monitor recovery after surgery in a convenient and noninvasive way.

“I think this is just the beginning. Devices are becoming much more sensitive and with many more capabilities,” study co-author Dr. Michael Snyder, professor and chair of genetics at Stanford’s School of Medicine, said in a statement. “As the technology continues to advance, people will be better equipped to understand what is going on with their own health in real time, just through their wearable devices.”

The study included 54 participants who wore a smartwatch that tracked heart rate, step count, skin temperature and electrical activity in the skin (to measure sweat production) over three years. They also had their vitals recorded via clinical heart rate monitors and blood tests that read blood cell count, glucose levels and other health indicators, which the researchers used to compare to smartwatch measurements.

The team learned that low electrical activity in the skin, or less sweat, as measured by smartwatches, was associated with dehydration, which blood tests revealed; alterations in heart rate discovered with a watch were able to predict changes in red blood cell count and hemoglobin, the molecule that carries oxygen throughout the body.

The researchers also found that rises in skin temperature and decreases in physical activity detected by smartwatches offered early signals that a person had higher immune cell counts, “an indication of an illness such as a cold or the flu.”

“It makes sense because if someone is getting sick, they may spike a fever, and they’re likely more tired and less active,” study co-lead Jessilyn Dunn, a former postdoctoral scholar at Stanford who is now an assistant professor at Duke University in North Carolina, said in the statement.

What the smartwatches couldn’t do, however, was accurately predict exact red blood cell count, the researchers said, but they could flag signs that red blood cells are running low — a sign of anemia.

“If you think about someone just showing up in an emergency room, it takes time to check them in, to get labs going and to get results back,” Dunn told UK Today News. “But if you were to show up in an ER and you’ve got an Apple Watch or a Fitbit, ideally you’d be able to pull the long-term data from that device and use algorithms to say, ‘this may be what’s going on.’”

“This experiment was a proof-of-concept, but our hope for the future is that physicians will be able to use wearable data to immediately get valuable information about the overall health of a patient and know how to treat them before the clinical labs are returned,” Dunn told the outlet. “There is a potential for life-saving intervention there if we can get people the right care faster.”

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