It may one day be possible to spot illness the same way many of us already track our exercise habits and sleep patterns: with wearable sensors, researchers say.
In a new study, 60 people wore devices that collected more than 250,000 measurements a day on things like heart rate, oxygen in the blood, activity levels, calories expended, sleep patterns and skin temperature.
After researchers got a baseline idea of normal readings for each person in the study, they looked for deviations from these typical patterns to see whether changes might be tied to new environmental conditions, illness, or other factors that can impact health.
The goal is a health dashboard that does for people what dashboards already do for cars, said senior study author Dr. Michael Snyder, director of the Center for Genomics and Personalized Medicine at Stanford University in California.
"Your car has 400 sensors, and dashboard lights go on when a problem occurs like the engine starts overheating or you are nearly running out of gas," Snyder said by email.
"In the future, you will have multiple sensors relaying information to your smartphone, which will become your health dashboard," Snyder added. "Alerts will go off with elevated heart rate over your normal level and heart beat abnormalities will be detected - these will enable early detection of disease, perhaps even before you can detect it yourself."
Altogether, Snyder and colleagues collected almost 2 billion measurements from the study participants, who each wore between one and seven commercially available activity monitors around the clock.
Snyder was one of the participants.
On a long flight for a family vacation last year, he noticed changes in his heart rate and oxygen levels. From previous trips with sensors, he knew his oxygen levels normally dropped during flights and his heart rate increased at the start of the flight but then returned to normal.
On this particular flight, however, his numbers didn't return to normal, and Snyder then went on to develop a fever and other signs of illness.
He had a hunch that it might be Lyme disease because he'd spent time outdoors in rural Massachusetts two weeks earlier and might have been bitten by a tick that transmitted the illness. He convinced a doctor to prescribe an antibiotic, then got tests results that confirmed a Lyme diagnosis.
For a few other participants, higher than normal readings for heart rate and skin temperature also turned out to signal a developing illness.
A few successful predictions don't mean the idea is ready for prime time, however. More research is needed before the snapshots of illness detection in the study might translate into gadgets people can purchase and use on their own. One device tested was recalled, and another didn't appear to work well, the authors note.
Just because people can monitor some vital signs right now on their smartphone or fitness tracker doesn't mean they can diagnose themselves without help from a doctor, noted Satchidananda Panda of the Salk Institute for Biological Studies in La Jolla, California.
"Many health enthusiasts will like this idea and will use the gadgets judiciously," Panda, who wasn't involved in the study, added by email. "However, the danger lies in the vast majority of lay users who misinterpret the data."
Because most patients only get vital signs checked at a physical or an appointment when they're sick or something goes wrong, though, wearable sensors might help doctors do a better job of detecting the onset of disease and monitoring its progression, said Dr. Karandeep Singh, a medical researcher at the University of Michigan in Ann Arbor who wasn't involved in the study.
"Physiological changes precede the development of symptoms for a variety of illnesses, and being able to detect these changes early may bring patients to attention much earlier when diseases are more readily treatable and potentially curable," Singh said by email.