Distraction was the greatest risk factor by far for new-onset acute low back pain (LBP), according to a new case-crossover study. The study in the issue of Arthritis Care & Research, also found that onset was most likely between 7:00 am and noon, that LBP risk was substantially increased by a number of modifiable physical and psychosocial triggers, and that people older than 60 years were less at risk from heavy loads than younger participants, perhaps because they have learned how to lift safely.
“The key message for clinicians is that even brief exposure to heavy loads and awkward postures will drastically increase our chances of developing back pain,” study coauthor Manuela L. Ferreira, PhD, associate professor at the George Institute for Global Health and the Institute of Bone and Joint Research, Sydney Medical School, University of Sydney, Australia, said. “In other words, not only people who are exposed to lifting activities on an ongoing basis are at risk. In addition, being distracted and fatigued during manual tasks will likely increase our risk of having back pain. The next step would be to develop and test prevention strategies based on these results.”
The researchers, led by Daniel Steffens, BPT, from the University of Sydney, recruited 999 patients with new episodes of acute LBP from 300 primary care clinics in Sydney, Australia, between October 2011 and November 2012. Subjects were asked to report exposure to 12 possible LBP triggers during the 96 hours before pain onset. Dr Ferreira said most of the included triggers have been listed as potentially hazardous activities in the Australian Code of Practice for the prevention of musculoskeletal disorders and added that the researchers also chose activities that could be modified and targeted in back pain prevention campaigns.
The possible physical triggers studied were “heavy load; awkward positioning; handling of objects far from the body; handling people or animals and unstable loading; a slip, trip, or fall; engagement in moderate or vigorous physical activity; and sexual activity.” The possible psychosocial triggers were alcohol consumption, fatigue, and being distracted during an activity or task. Patients were interviewed by telephone within 7 days of presenting with acute LBP, using a guided interview script that included date and time of pain onset as well as time and duration (if any) of exposure to each of the 12 possible triggers.
The researchers used a case-crossover design, so that each person served as his or her own control; the design aims to reduce the potential for between-person confounding and to eliminate potential confounders such as genetic and lifestyle influences.
The greatest risk for an episode of acute LBP was associated with the psychosocial trigger of being distracted during a task or activity, which had an odds ratio (OR) of 25.0 (Table). All of the physical triggers except sexual activity were strongly associated with increased risk for back pain, with ORs ranging from 8.0 to 2.7. The most dangerous physical trigger was manual tasks involving awkward positioning. In addition, alcohol consumption was not linked to increased risk of LBP.
“While many of the triggers included in the study had been previously seen as hazardous activities, especially in the workplace, we were surprised that being distracted and fatigued during manual tasks will drastically increase our chances of developing back pain,” Dr Ferreira said.
An unexpected finding was a diurnal variation in LBP pain onset. The authors write that 35.2% of participants reported pain onset between 7:00 and 10:00 am. This inspired exploratory post hoc analyses of risk associated with being exposed to triggers between 7:00 am and noon vs between 1:00 pm and 6:00 pm. Although the study lacked sufficient power to completely resolve this issue, the researchers found that both morning exposure to awkward posture and manual tasks involving unstable loading in the morning were strongly associated with risk for LBP onset.
Dr Ferreira said, “While we are not sure why back pain risk is highest in the morning, a possible explanation is that spinal discs swell with fluid overnight, and therefore the lower back will be more susceptible to stress and strains in the morning.”
The researchers found no interaction between any trigger and habitual participation in physical activity, body mass index, number of previous LBP episodes, depression, or anxiety. The interactions analysis did reveal that the OR associated with manual tasks involving heavy loads decreased from 13.6 (95% confidence interval [CI], 5.4 – 34.5) at 20 years to 2.7 (95% CI, 1.5 – 4.7) at 60 years. “One potential reason for this may be that older people have learned to lift correctly or are more careful when handling heavy loads,” the authors write.
“This is an excellent study, carefully and cleverly designed, well-powered, and well-reported by a great team with well-known world experts on the topic of [LBP],” Wolf E. Mehling, MD, associate professor of clinical family and community medicine, Osher Center for Integrative Medicine and Department of Family and Community Medicine, University of California, San Francisco, who was not involved in the study, told Medscape Medical News. “The strongest triggers were postural (how a manual task was done) and inattention towards the task at the moment of the task. The former is not really major news, as back school programs and occupational prevention programs are aware of this. The latter sounds trivial but may be a major topic, as present-moment awareness and mindfulness could be preventive measures.”
Dr Mehling suggested that morning hours and younger age may be associated with “a belief that one can do whatever one wants, a sense of having no limits, which with maturation of individuals or sustained back problems may slowly wane.”
He added, “It is very reassuring is that sex is not a trigger and that getting older may not be a problem.”
The researchers point out that their findings have major public health implications, highlighting the need for research on programs that modify the LBP triggers. They write, “[T]he burden of disease due to road traffic injury is far less than that for back pain, yet many countries devote considerable resources to controlling behaviors that increase the risk of road crashes.”
Dr Ferreira said, “For the first time, we were able to identify that brief exposure to hazardous activities will increase the risk of developing a sudden episode of moderate to severe back pain, strong enough to lead you to seek care for it. Until now, back pain was believed to be associated only with repetitive and ongoing exposure to these activities, so our results add important information on the length of exposure. We also add important information on the role of being fatigued and distracted while engaged in physical tasks, as this will dramatically increase our risk of developing back pain.”
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