Study: Back belts reduce injuries by one-third
Largest sample to date
A six-year study of 36,000 Home Depot workers has shaken up the lukewarm debate over the preventive efficacy of back support belts.
The study, which covered a total of 101 million hours worked during the period 1989-1994, reported the following:
• Use of back support belts reduced lower back injuries by 34%, with benefits across all age groups.
• Wearing back supports greatly impacted employees during their first two years with the company, reducing back injuries 69% for men and 67% for women.
• The use of back supports was most beneficial for men, employees under 25 or over 55, and employees with jobs requiring heavy lifting.
These findings are in conflict with those of several earlier, smaller studies. In fact, existing literature at the time (1994) prompted The National Institute for Occupational Safety and Health to issue its own report suggesting little evidence to support the use of the belts. (See the story, above.)
The new study’s lead author, Jess F. Kraus, MPH, PhD, of the Southern California Injury Prevention Research Center, School of Public Health, University of California, Los Angeles, was himself skeptical going into the study, which was released in December 1996. "The literature on the subject was far from being conclusive," he notes. "It’s fair to say I was surprised. I went into the study realizing there just was no compelling evidence to believe that [back support belts] would work in real-life settings."
It’s more than the sample size
Kraus says several aspects of the report give it more weight than existing literature. "Most research of the epidemiologic variety depends on what we call observational data. We do not experiment with human beings; we have to observe what goes on in the natural world," he explains. "This methodology had several strong points. One, obviously, was the size of the workforce. Then, there was the ability to differentiate within the workforce in terms of employee hours using and not using back supports." (During the first year studied, 1989, no Home Depot employees wore the supports. Injury statistics for that year were compared to the five following years, when mandatory usage was company policy.)
In addition, says Kraus, the ability to identify and obtain all injury claim records from Home Depot was a significant plus. "In other words, the company did not select and hand records to us there then would have been some potential selection bias," he observes.
Home Depot was already committed to the belt supports, despite the lack of scientific evidence in 1989, notes Steve Taylor, MBA, corporate safety manager. "My predecessor [Taylor joined the company in 1991] had conducted a small pilot program with a Midwest competitor of ours, which convinced him they could provide a safety advantage. It was his idea to bring them on as policy."
That policy, plus a positive corporate culture, led to an astounding 98% compliance rate for the period of the study, which may lend even more weight to the findings.
"We’re very happy the [results] came out like they did; we gave them our data and didn’t know what was going to come out," Taylor recalls. "We wanted it to be an arm’s length kind of thing, and it really was."
More research is needed
Despite the impressive results, Kraus cautions against reading any universal implications into the study. "The study population was material handlers doing rather prescribed tasks over a six-year period, and those tasks did not change much," he notes. "Therefore, I would be extremely cautious about the extension of the findings to work groups who were not material handlers [people who lift and carry products and supplies]."
In other words, says Kraus, it would be inappropriate to suggest that every worker could be protected by back belt supports. "The study . . . raises the need to examine these findings in light of different job requirements," he says, noting that he and his research team are beginning to set up studies of different groups of workers. (Another leading back injury expert is less sanguine about the results of the UCLA study. See story, above.)
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