By Julie Appleby, Kaiser Health News

Workplace wellness programs have become an $8 billion industry in the U.S. But a study published Tuesday in JAMA found they don’t cut costs for employers, reduce absenteeism or improve workers’ health.

Most large employers offer some type of wellness program — with growth fueled by incentives in the federal Affordable Care Act.

A host of studies over the years have provided conflicting results about how well they work, with some showing savings and health improvements while others say the efforts fall short.

Many studies, however, faced a number of limitations, such as failing to have a comparison group, or figuring out whether people who sign up for such wellness programs are somehow healthier or more motivated than those who do not.

Now researchers from the University of Chicago and Harvard may have overcome these obstacles with one of the first large-scale studies that is peer-reviewed and employs a more sophisticated trial design.

They randomly assigned 20 BJ’s Wholesale Club outlets to offer a wellness program to all employees, then compared results with 140 stores that did not.

The big-box retailer employed nearly 33,000 workers across all 160 clubs during the test.

After 18 months, it turned out that yes, workers participating in the wellness programs self-reported healthier behavior, such as exercising more or managing their weight better than those not enrolled.

But the efforts did not result in differences in health measures, such as improved blood sugar or glucose levels; how much employers spent on health care; or how often employees missed work, their job performance or how long they stuck around in their jobs.

“The optimistic interpretation is there is no way we can get improvements in health or more efficient spending if we don’t’ first have changes in health behavior,” said one study author, Katherine Baicker, dean of the Harris School of Public Policy at the University of Chicago. (Dr. Zirui Song, an assistant professor of health policy and medicine at Harvard Medical School, was its co-author.)

“But if employers are offering these programs in hopes that health spending and absenteeism will go down, this study should give them pause,” Baicker said.

The study comes amid widespread interest in wellness programs.

The Kaiser Family Foundation’s annual survey of employers found that 53% of small firms and 82% of large firms offer a program in at least one of these areas: smoking cessation, weight management and behavioral or lifestyle change. (Kaiser Health News is an editorially independent program of the foundation.)

Some programs are simple, offering gift cards or other small incentives to fill out a health risk assessment, take a lunch-and-learn class or join a gym or walking group. Others are far more invasive, asking employees to report on a variety of health-related questions and roll up their sleeves for blood tests.

A few employers tie financial incentives to workers actually lowering risk factors, such as high blood pressure or cholesterol — or making concerted efforts to participate in programs that might help them do so over time.

The Affordable Care Act allowed employers to offer financial incentives worth up to 30% of the cost of health insurance, leading some employers to offer what could be hundreds or even thousands of dollars off workers’ deductibles or premiums to get them to participate. That led to court challenges about whether those programs are truly voluntary.

In the study reported in JAMA, the incentives were modest. Participants got small-dollar gift cards for taking wellness courses on topics such as nutrition, exercise, disease management and stress control. Total potential incentives averaged $250. About 35% of eligible employees at the 20 participating sites completed at least one module.

Results from those workers — including attendance and tenure data, their self-reported health assessment and results from lab blood tests — were specifically compared with similar reports from 20 primary comparison sites where workers were not offered the wellness gift cards and classes. Overall employment and health spending data from all worksites were included in the study.

Wellness program vendors said details matter when considering whether efforts will be successful.

Jim Pshock, founder and CEO of Bravo Wellness, said the incentives offered to BJ’s workers might not have been large enough to spur the kinds of big changes needed to affect health outcomes.

Amounts of “of less than $400 generally incentivize things people were going to do anyway. It’s simply too small to get them to do things they weren’t already excited about,” he said.

An accompanying editorial in JAMA noted that “traditional, broad-based programs like the one analyzed by Song and Baicker may lack the necessary intensity, duration, and focus on particular employee segments to generate significant effects over a short time horizon.”

In other words, don’t give up entirely on wellness efforts, but consider “more targeted approaches” that focus on specific workers with higher risks or on “health behaviors [that] may yield larger health and economic benefits,” the editorial suggested.

It could be, the study acknowledges, that 18 months isn’t enough time to track such savings. So, Baicker and Song also plan to publish three-year results once they are finalized.

Still, similar findings were recently reported in another randomized control trial conducted at the University of Illinois, where individuals were randomly selected to be offered wellness programs.

In one interesting point, that study found that wellness-program participants were likely already healthier and more motivated, “thus a primary benefit of these programs to employers may be their potential to attract and retain healthy workers with low medical spending.”

Everyone involved in studying or conducting wellness agrees on one thing: Changing behavior — and getting people motivated to participate at all — can be difficult.

Steven Aldana, CEO of WellSteps, a wellness program vendor, said that for the efforts to be successful they must cut across many areas, from the food served in company cafeterias to including spouses or significant others to help people quit smoking, eat better or exercise more.

“Behavior is more complicated than simply taking a few wellness modules,” said Aldana. “It’s a lifestyle matrix or pattern you have to adopt.”

Kaiser Health News, a nonprofit health newsroom whose stories appear in news outlets nationwide, is an editorially independent part of the Kaiser Family Foundation