Is Heavy Lifting a Risk Factor for Low Back Pain?Everyone believes that lifting heavy objects or even lifting light to moderately heavy objects when done repeatedly can cause low back pain. But does it really? Or is it more a matter that the back pain would have happened anyway and it was just noticed for the first time while lifting?
These are the questions posed by a group of epidemiologists from seven different medical research institutions in Canada. Epidemiologists are researchers who collect data over time and look for trends. In this study, they reviewed studies already published in what is called a systematic review.
By systematically searching various medical libraries, health journals, and even unpublished reports they were able to come up with 2,766 different studies related to these questions. They used specific search terms such as low back pain, occupational setting, work place, and lifting to find what they were looking for.
Thirty-five (35) studies met the criteria they had set up before starting the search. As the search terms suggest, that criteria included studies written in English or French related to low back pain, occupational lifting, and cause of low back pain. Each study had to have at least 30 subjects for the findings to be statistically significant.
There were many details reviewed from these studies: types of lifting, amount of weight lifted, severity of back pain, and whether or not sick leave was used. There was a broad range of specific occupations studied (e.g., nursing, retail salespersons, heavy manual laborers, administrators). The studies were conducted in 16 different countries including the U.S., Sweden, Russia, South Africa, Denmark, China, Turkey, Canada, The Netherlands, Nigeria, the United Kingdom, and India.
When all the data was analyzed, there simply wasn't enough evidence to show a direct causal relationship between occupational lifting and the development of low back pain. There was one study that suggested regularly lifting more than 25 kg (70 pounds) was associated with low back pain. But unless this finding is found in other studies, it's not enough to say for sure one (lifting) is the cause of the other (back pain).
The authors of this systematic review also point out that one of the major problems in conducting a review of this type is the poor quality of studies being reviewed. They don't all use the same outcome measures. So it's difficult to pool the data and make any sense out of it.
Different studies look at different factors but it's difficult to analyze all the various possible reasons why workers experience back pain while lifting. Besides the obvious (lifting a heavy object), there may be twisting, bending, or awkward postures involved. Age and gender (male versus female) could be possible factors.
And what about the size of the object, whether the object was being picked up or lifted overhead, use of handles and the distance the object was carried after lifting. What about factors like which shift the worker was on when the injury occurred (day, evenings, nights) or when during the shift the pain started (early, mid, late)?
You might wonder why it's even necessary to conduct studies like this one. Common sense tells us that heavy lifting can result in low back pain. But from an epidemiologist's point-of-view, cause and effect with these two things (lifting and back pain) must be proven not just suspected. It could be coincidental that lifting precedes back pain. Or there could be a group of factors that must occur all at the same time to result in low back pain.
And public policy regarding work guidelines come from studies like this one. Clearly, low back pain in the working population accounts for a large portion of sick leave, lost wages, lost productivity, and high medical costs. Public health officials have a duty and responsibility to make decisions based on an accurate understanding of risk and result.
Right now, spine physicians simply can't prove (or disprove) that low back pain is caused by work-related lifting activities. Future studies must continue to look for directly linked risk factors for low back pain that develops on-the-job. The goal to prevent these episodes cannot be achieved by putting into place strategies that are based on beliefs or even on what seems logical. Evidence to support public health guidelines is a must.
Eugene K. Wai, MD, MSc, FRCSC, et al. Causal Assessment of Occupational Lifting and Low Back Pain: Results of a Systematic Review. In The Spine Journal. June 2010. Vol. 10. No. 6. Pp. 554-566.
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