The "big data" app that predicts employees' health

Some employers are turning to data -- lots of it -- to help them reduce their costs of providing employees with health insurance. But some experts worry that such technology could prove intrusive, allowing companies to pry into workers' medical history.

One corporate giant using "big data" for health purposes is Walmart (WMT), the world's largest retailer. It is an early customer of Castlight Health (CSLT), whose app collects medical data on workers and then nudges them with information that could help them make the best care decisions.

In one example, the app tracks female employees who have stopped filling their birth control prescriptions, and then matches that information with a woman's age. The app then sends them messages about how to find an OB/GYN to help them with prenatal care.

If that seems invasive, you're not alone -- the app has raised ethical concerns about how employers might use that information. Castlight says that personal data about individual workers isn't relayed to employers, which guards against managers learning who might be at risk for diabetes or who is thinking about having a child, among other scenarios.

"We present them the number of people in that segment," said Alka Tandon, the lead product manager on the Castlight product. "We'll tell them 200 employees across the organization are considering surgery, but they can't drill down and say it was Jane Smith."

That might reassure some, but others aren't convinced. University of Maryland law professor Frank Pasquale tells The Wall Street Journal that such programs carry "enormous potential risks" for exposing personal health data to companies.

Under the Health Insurance Portability and Accountability Act of 1996 (HIPAA), employers aren't allowed to access a worker's personal medical information. But there's more leeway when it comes to data mining, aggregating information and tapping data that doesn't personally identify a worker.

Meanwhile, the risk of workers being discriminated against on the job due to medical issues or pregnancy remains all too real, statistics show. In 2013, alleged pregnancy discrimination prompted more than 5,000 complaints with the Equal Employment Opportunity Commission. And pregnancy discrimination charges are increasing, with the number of allegations rising by about one-third during the past decade, according to the National Partnership for Women & Families.

Such concerns aren't stopping a growing number of employers from tracking their workers' health, offering Fitbits or standing desks. One group is urging companies to report statistics about their employees' health as another financial metric that shareholders can judge them by, on the theory that a fitter workforce is a stronger one.

Castlight's Tandon said that workers can opt out of the program, although she didn't have data on the share of employees who have done so. The early results of the program, which is only three months old, have shown that workers are using their health plans more effectively, she added.

As for the possibility that the the company's software, which is available on an app and on Castlight's website, might strike workers as creepy, Tandon said she "understands the concern." She added that the company tests its messages before rolling them out, to make sure that they won't offend or rub workers the wrong way.

"We built the product with those concerns in mind," she said. "We made sure the employer doesn't have access to personal employee information."