Prospective longitudinal cohort study.
To determine the associations for workload and health-related factors with incident and recurrent low back pain (LBP), and to determine the mediating role of health-related factors in associations between physical workload factors and incident LBP.
It is not known whether the risk factors for the development of LBP are also prognostic factors for recurrence of LBP and whether the associations between physical workload and incident LBP are mediated by health-related factors. We used data from the Swedish Longitudinal Occupational Survey of Health study. Those responding to any two subsequent surveys in 2010 to 2016 were included for the main analyses (N = 17,962). Information on occupational lifting, working in twisted positions, weight/height, smoking, physical activity, depressive symptoms, and sleep problems were self-reported. Incident LBP was defined as pain limiting daily activities in the preceding three months in participants free from LBP at baseline. Recurrent LBP was defined as having LBP both at baseline and follow-up. For the mediation analyses, those responding to three subsequent surveys were included (N = 3516).
Main associations were determined using generalized estimating equation models for repeated measures data. Mediation was examined with counterfactual mediation analysis.
All risk factors at baseline but smoking and physical activity were associated with incident LBP after adjustment for confounders. The strongest associations were observed for working in twisted positions (risk ratio = 1.52, 95% CI 1.37, 1.70) and occupational lifting (risk ratio = 1.52, 95% CI 1.32, 1.74). These associations were not mediated by health-related factors. The studied factors did not have meaningful effects on recurrent LBP.
The findings suggest that workload and health-related factors have stronger effects on the development than on the recurrence or progression of LBP, and that health-related factors do not mediate associations between workload factors and incident LBP.
Level of Evidence: 3
Lifting heavy loads or working in twisted positions and health-related factors increased the incidence of low back pain (LBP). The associations between workload factors and incident LBP were not mediated by health-related factors. Associations for prognostic factors of recurrent LBP were weaker than those for incident LBP.
∗Stress Research Institute, Stockholm University, Stockholm, Sweden
†Finnish Institute of Occupational Health, Helsinki, Finland
‡Department of Public Health, University of Helsinki, Helsinki, Finland.
Address correspondence and reprint requests to Jaana I. Halonen, PhD, Finnish Institute of Occupational Health, 70032 Työterveyslaitos, Finland; E-mail: firstname.lastname@example.org
Received 7 December, 2018
Revised 7 February, 2019
Accepted 5 March, 2019
The manuscript submitted does not contain information about medical device(s)/drug(s).
The Swedish Research Council and the Academy of Finland (Grants #287488, #294096 and #319200) funds were received in support of this work.
Relevant financial activities outside the submitted work: grants.
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