New technology worn on the body can help medical professionals determine if someone is becoming ill or if a disease is developing.

Soon your doctor may be able to tell what’s wrong with you before you make an appointment.

Wearable biosensors could make this possible.

Biosensors monitor vital signs that reveal much about what is going on inside the body. Serious problems that are detectable include the onset of infection, inflammation, and insulin resistance.

A team of researchers from Stanford University revealed these discoveries in a study published today in PLOS Biology.

Michael Snyder, Ph.D., professor and chair of genetics at Stanford, is the senior author of the study, along with lead postdoctoral co-authors Xiao Li, Ph.D., and Jessilyn Dunn, Ph.D., and software engineer Denis Salins.

Snyder and his colleagues began their ongoing study in 2014 with 60 subjects ranging in ages from 28 to 72, divided equally by gender. Snyder is one of his own study participants and wears seven sensors.

“We wear various types of smart watch monitors 24 hours a day,” Snyder told Healthline. “Some people have been wearing these devices for up to two-and-a-half years now.”

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The first smart watches became available in 2013, and the study began to use Basis watches when they debuted in 2014.

Today, Snyder’s subjects use the Moves app and smart watches that collect data on an iPhone, and then send anonymized information directly to a database.

“There are a large number and wide variety of these devices for different uses,” Snyder said. “The smart watch measures heart rate, activity — steps or running — and skin temperature. Some, like the Moves app, are right on your cell phone. The Basis device is a smart watch you wear on your wrist. You place the SpO2 blood oxygen monitor on your finger. You place the Dexcom on your skin and it measures glucose levels. I even use a radiation monitor that measures radiation sensitivity.”

In related work at Stanford, Snyder said that Ronald Davis and Lars Steinmetz, professors of genetics, are building a device that measures sweat.

Snyder and his team collected nearly 2 billion measurements from participants. The information included continuous feeds of data from each person’s wearable biosensors, as well as periodic data from laboratory tests of their blood chemistry, gene expression, and other measures.

Study subjects wore from one to seven commercially available activity monitors and other devices that collected more than 250,000 measurements a day.

The data included weight, heart rate, blood oxygen, and skin temperature. The monitors also recorded activities such as sleep, steps, walking, biking, and running. Other data included calories burned, acceleration, and even exposure to gamma rays and X-rays.

Snyder said that an important aspect of their approach was to establish a range of normal, or baseline, values for each person studied.

“We want to study people at an individual level,” he said.

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Biosensors have a bright future.

“Wearable devices and sensors are certainly reaching the attention of the lay public, whether it’s watches from Apple or Fitbit, or sleep trackers and sensors that monitor breathing and heart rate,” Dr. Atul Butte, told Healthline.

Butte is director of the Institute for Computational Health Sciences, and a distinguished professor of pediatrics at the University of California, San Francisco (UCSF). “I think some individuals that try to get healthy and stay healthy use these devices to help reach their goals.”

Butte credits his own 50-pound weight loss to gadgets from Fitbit.

“In medical science, it means that we might be able to study patients better within their own home environment,” he said. “Perhaps a clinical trial of the future, testing the effect of a potential new drug, might draw upon data that patients provide themselves, like effects on mood or sleep or diet, through their devices.”

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A personal medical experience showed Snyder the value of his research.

“Last year I helped my brother put up fences in a Lyme-infected area of Massachusetts,” he said. “Two weeks later when flying to Norway, I noticed my blood oxygen levels were much lower than normal, and they did not return to normal upon landing.

“These were both detected using [the seven] portable devices. I knew this was not quite right and suspected I might be getting ill. Over the next several days, I developed a low-grade fever and then visited a physician in Norway who gave me doxycycline, which cleared the infection. Lyme disease was subsequently confirmed.”

Snyder was impressed that the wearable biosensors pointed to an infection before he even knew he was sick. “Wearables helped make the initial diagnosis,” he said.

Later analysis confirmed his suspicion that the deviations from his normal heart rate and oxygen levels on the flight to Norway had indeed been abnormal.

Snyder’s team wrote a software program for data from a smart watch called Change of Heart to detect deviations from participants’ baseline measurements and to sense when people were becoming sick.

The devices were able to detect common colds as well as help identify Snyder’s development of Lyme disease.

The most crucial value of biosensors may be their early warning potential.

The Stanford scientists say their study points to the important possibility of identifying inflammatory disease in people who may not even know they are getting sick.

Data from several subjects showed that higher-than-normal levels for heart rate and skin temperature correlated with increased levels of C-reactive protein in blood tests. C-reactive protein, an immune system marker for inflammation, often indicates infection, autoimmune diseases, developing cardiovascular disease, or even cancer.

Snyder’s own biosensors revealed three different bouts of illness and inflammation, in addition to the Lyme disease infection. His devices also showed that he was unaware of another infection until he saw his sensor data, which revealed an increased level of C-reactive protein.

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Butte says other diseases may be detectable with biosensors.

“Many of these devices focus on vital signs, such as pulse rate and body temperature, so diseases that alter those might be the easiest to detect, like infectious diseases or even reproductive disorders,” he said. “Several chronic diseases are known to present with frequent ‘flares,’ like multiple sclerosis and inflammatory bowel disease. And maybe those could be detected earlier to enable corrective therapeutics. Psychological or mood disturbances might be detectable as well.”

At the UCSF Institute for Computational Health Sciences, Butte and his colleagues are using all the data available on patients to help develop diagnostics or therapeutics, or simply to better understand diseases.

Some examples of sensor work include the Health eHeart study, which looks at heart rate and heart rhythm to detect heart disease sooner, he said.

UCSF researchers, patients, and families are also looking at more sophisticated types of sensors, Butte said, such as the glucose monitors given to people with type 1 diabetes, and are learning from those measurements.

“Going beyond the sensors that actually touch the body, smart phones also have great cameras, and there is work going on to use those cameras and pictures to diagnose diseases sooner,” Butte said. “I think if one can get to body fluids, like blood, saliva, and urine, there is a much wider range of detectability.”

UCSF also has a Center for Digital Health Innovation where more of these technologies are being developed, he said.

Snyder looked at the practical aspects of using sensor-collected health data.

“The information collected could aid your physician, although we can expect some initial challenges in how to integrate the data into clinical practice,” he said. “Some patients may want to protect the privacy of their physiologic data, or may want to share only some of it.

“We are trying to implement data-driven health — using data to follow people when they are healthy, and then detect when they become ill at the earliest possible time.”