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Is that FitBit or FuelBand actually doing your patient or you any good? The first studies are gearing up to find out.

Such wirelessly-networked body sensor devices that connect via Bluetooth to a smartphone or tablet have seen an explosion in popularity such that the number manufactured is expected to well exceed the U.S. population within the year, based on data from the U.S. Census Bureau and market research firm .

The idea is that the tracking and feedback motivates healthy behaviors and thus outcomes. Some devices are also billed as giving clinicians another tool to inform clinical management.

"There are a lot of good reasons to think mobile health devices will improve outcomes but the hard evidence to support that is for the most part lacking," explained , who studies mobile health devices and apps as director of the digital medicine program at Scripps Health in La Jolla, Calif.

What's to Prove?

The open question with most biometrics is whether the surrogate measures they track are actually meaningful, noted Euan Thomson, PhD, CEO of AliveCor, which makes an iPhone-linked, single-lead electrocardiogram ().

Take for example activity trackers like the FitBit and FuelBand.

"If you count the number of steps, it doesn't tell you anything other than the number of steps," he told 番茄社区. "It doesn't tell you are you going to live longer, are you going to lose weight, are you going to get sick less?"

The ideal would be behavior modification to make people increase their physical activity, but there's a question of causality, Steinhubl added.

Studies have linked an increase in daily step counts to preservation of insulin sensitivity and to a small but significant .

But those studies weren't randomized comparisons of a pedometer or activity tracker versus none. All had their activity tracked the same way, but some were more motivated to make changes than others.

"Often the people who get FitBits and such are already motivated to be more active and would likely do it anyway," Steinhubl said.

For clinicians, reports and readouts of physical activity, ECGs, or home blood pressure are only useful if the data can be acted on in a meaningful way, he added.

"Taking it to the next level and creating real healthcare value is something I think people have to take quite seriously," Thomson agreed. "Otherwise all of these devices will really just be a fad."

More Is Better?

Beyond the unknown benefit, we shouldn't assume that all the extra data is benign either, cautioned , MPH, an internist at Dartmouth University in Hanover, NH, and a .

"We're at a place where we're often uncritical about the value of more data points," he explained. "Sometimes we respond to data in undesirable ways. It can be alarming and it can initiate unnecessary interventions."

That's especially true of chronic conditions, Steinhubl agreed.

In one study, , he noted.

"I'm sure it would be the same if we ever did a study [in which] somebody with high blood pressure had to wear a blood pressure cuff everywhere they went and interrupt what they're doing," he explained. "In my experience as a clinician, people with chronic illnesses don't like being reminded that they have chronic illnesses."

On the other hand, Thomson noted that people using his company's iPhone ECG tend to say it's a tool for peace of mind.

"They want to know whether they have atrial fibrillation," he explained. "They are more likely to worry if they don't know than if they do."

Another concern is how to integrate the app and sensor data into clinical care.

Some mobile health devices allow a report to be sent to a clinician; others could be shown at office visits.

For clinicians, though, it's not an easy matter of how to incorporate that new data stream into patient care, Steinhubl noted.

Most clinicians "at face value look at mobile technology as more work with no reimbursement to the healthcare system," he said.

It could drive up healthcare costs too, Welch noted.

He pointed to research in heart failure patients attempting to use electrical impedance sensed by defibrillator leads in the heart as an early sign of fluid overload, but which didn't help survival but drove up clinic visits and hospitalizations.

Where's the Data?

One large-scale proving ground for mobile health devices and apps will be the , with a planned 1 million participants. (See 'Big Data' No Small Challenge for Health eHeart Study.)

For example, a planned substudy will attempt to link activity levels measured by the FitBit before and after bladder cancer resection to patients' long-term outcomes, according to , project director for the study from its headquarters at the University of California San Francisco.

A second would compare outcomes and lifestyle changes for participants given a bundle of devices -- a Bluetooth blood pressure cuff, a scale, a smartphone app for their diet and heart monitor -- for 6 months versus another group that doesn't get the bundle until later.

Another trial is Scripps' testing whether a bundle of blood pressure cuff, glucose monitor, and heart monitor could cut unplanned healthcare visits among 200 chronic disease patients identified as high resource users.

Industry partnership studies are also underway, such as a using that company's app to passively monitor behavior via GPS, accelerometer, and text and voice call logs along with periodic surveys as measures of symptoms in adolescents with Crohn's disease and ulcerative colitis, with the hope of monitoring treatment effectiveness.

Ginger.io has its own .

With such research informing use, Steinhubl projected mobile health devices "will every year play a bigger and bigger role in helping us better understand the disease processes in individuals as well as better manage the health of those individuals."

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