But chronic stress that doesn't go away when the emergency passes costs the U.S. economy an estimated $300 billion, according to one often-cited tally, in everything from elevated blood pressure and stroke risk to absenteeism and employee turnover.

Now a Twin Cities company called the Oxygen Plan Corp. is tapping expertise from the Mayo Clinic to develop what is supposed to be the first mobile app to objectively measure a person's level in a single stat: the Stress Number.

The goal is to help companies and workers get a better handle on stress levels, and find mitigation strategies before larger costs mount.

This week, the Oxygen Plan, based in St. Louis Park, announced its agreement with the Mayo Clinic's technology outreach arm, Mayo Clinic Ventures.

"Managing stress is one way to keep patients from becoming patients in the first place," Mayo Clinic oncologist Dr. Ed Creagan, who will be working on the project, said in a statement. "Everyone should know the impact that stress is having on his or her life."

Under the agreement, Mayo will provide clinical expertise to refine the Stress Number methodology and develop the mobile app. The Oxygen Plan and Mayo declined to release details of the licensing agreement, but a Mayo Ventures spokesman said the organization typically gets an equity stake in companies it works with in such deals, and may also get future royalties from sales.

In addition to seeing the app available to the wider public, Mayo may end up using the app to measure stress of its own employees, Mayo Clinic Ventures Chairman Jim Rogers said.

The stress assessment program, already available via a standard Web browser, works by asking users a series of 30 questions that generate three scores gauging a person's stress at home, at work, and in their social life. The quiz is supposed to take about five minutes.

Observers like Jim Ayers, a longtime Minneapolis clinical psychologist who isn't affiliated with the company, said the application seems like a natural extension of mobile technology into the realm of health care.

"Knowledge is power. If people have relevant knowledge in a timely way, they can do something about it," said Ayers, who is working on mobile health technology for a different organization. "I see this as just part of a bigger picture and a move toward making medical technology more accessible and practical to people."

The app should allow doctors to treat more patients remotely, while gathering de-identified data that could be used to support future empirical analyses, Ayers said.

The software doesn't appear to need approval from the Food and Drug Administration, the company said.

Rogers said stress-measurement tools are intended as one way to address a complex problem. "It might be a way to bring down cost, and communicate better with patients, and bring down stress and burnout," he said.

Right now, the Oxygen Plan's biggest clients are employers who are trying to watch health care costs.

Company executives declined to disclose the per-worker fees they charge to make the tool available to health plans and employers. But the company wants to expand the technology to make the Stress Number a standard measurement tool in all health-risk assessments.

"We would love this to be a world metric, globally," Oxygen Plan CEO Eric Lucas said. "We give people a point of clarity unlike anything they have seen before, so our engagement stats are pretty high."

Joe Carlson • 612-673-4779