The prognostic value of depressive symptoms, fear-avoidance, and self-efficacy for duration of lost-time benefits in workers with musculoskeletal disorders

Freek Lötters ^1*, Renée-Louise Franche ², Sheilah Hogg-Johnson ³, Alex Burdorf ⁴ and Jason D Pole ³

¹ AStri research and consultancy agency, Netherlands
² institute of Work & Health, Canada
³ Institute of Work & Health, Canada
⁴ Department of Public Health, Netherlands

^* To whom correspondence should be addressed. E-mail: f.lotters{at}astri.nl.

Accepted 22 February 2006

Abstract

Background. The psychological factors of depressive symptoms, fear avoidance, and self-efficacy are deemed to be important in the work disability process. However, the prognostic value of these factors for time on benefit is not well understood. Aims. To analyse the prognostic value of psychological factors for the number of days on total compensation benefit during 12 months. Methods. In a longitudinal study of 187 workers receiving total compensation benefits due to musculoskeletal disorders, we analysed the prognostic value of psychological factors measured 4 to 5 weeks post-injury for duration on total compensation benefit over 12 months. Cox Proportional Hazard regression analyses were conducted. Special emphasis was given to variable selection and to the analysis of confounding effects of potential prognostic variables. Results. The final model indicated that increased depressive symptoms and poorer physical health significantly increase the number of days on total benefit. Confounders included in the final model were pain, and fear of income loss. In the final model the impact of fear-avoidance ceased to be significant when work related variables were included in the fully adjusted model. This illustrates that interrelationships between variables must be taken into account when building multivariate prognostic models. The addition of work related variables to the model did not result in any major changes in the adjusted model, which suggests that when measured 4 to 5 weeks post-injury, psychological and physical health factors are strong predictors of time on benefits, while work conditions are less important. Conclusion. The present study supports that the presence of depressive symptoms and poor physical health in workers on benefit due to musculoskeletal disorders increases the number of days on total compensation benefits significantly, when controlling for confounding variables.

Keywords: Confounding effects, Musculoskeletal disorders, Psychological factors, Return to work

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