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Title:Determinants of Chronic Disability Related to Low Back Pain: Structural Equation Modeling of an Integrative Model.

Authors and affiliation: Manon Truchon1,2, Lise Fillion3, Ginette Truchon4, Clermont Dionne2,5, Bertrand Arsenault6, Claude Viau7, Denis Côté2

1 Département des relations industrielles, Université Laval, Québec, Canada
2 Centre interdisciplinaire de recherche en réadaptation et intégration sociale (CIRRIS), Québec, Canada
3 Faculté des sciences infirmières, Université Laval, Québec, Canada
4 Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montréal, Canada
5 Département de réadaptation, Université Laval, Québec, Canada
6 Ecole de réadaptation, Université de Montréal, Montréal, Canada
7 Département de santé environnementale et santé au travail, Université de Montréal, Montréal, Canada

Email address: manon.truchon@rlt.ulaval.ca

Introduction: We propose a model for the integration of the psychosocial determinants of chronic low back pain (LBP) that have been identified in prospective studies. The biopsychosocial model of the stress process was adapted to the LBP problem and tested using structural equation modeling. The biopsychosocial model of the stress process is similar to specific LPB models but it is more global by incorporating the environmental and biological components of the stress process.

Objectives: To verify the value of the theoretical stress process model to explain chronic disability.

Methods: In a longitudinal prospective design, 439 workers on sick leave due to an occupational low back pain were evaluated during the sub‑acute stage of LBP and six months later. Their evaluation was based on the following variables: number and intensity of stressors, pain, control of pain, catastrophizing, fear of movement, fear of work, depression, anxiety, anger, behavioural coping, functional limitations, and on an exploratory basis, organisational support, salivary cortisol, interleukin-6 and dehydroepiandrosterone sulphate (DHEA-S).

Results: Confirmatory factor analyses allowed to test and modify the measurement model which is finally composed of the following factors: Environmental Demand, Fear of Movement, Psychological Distress, Avoidance Coping and Functional Limitations. During the sub‑acute stage, structural analyses confirmed that: a) Environmental demand (,32) and Fear of movement (,28) increased Distress (r2 = ,24); b) Distress (,49) and Fear of movement (,28) increased the use of Avoidance coping (r2 = ,42); c) Distress (,22) and Avoidance (,58) increased Functional Limitations (r2 = ,54). Longitudinal structural analyses revealed that functional limitations at the chronic stage were explained by sub‑acute functional limitations (,32), fear of movement (,18) and distress (,13) (r2 = ,21). Biological variables and organisational support were left out of the model due to modest correlations with functional limitations. In separate regression analyses, organisational support was not related directly to functional limitations but indirectly through fear of work.

Conclusion: This biopsychosocial model allowed the integration of anterior evidence and the proposal of causal processes in the transition from sub‑acute to chronic pain. It also provides a framework to help target modifiable risk factors of chronic disability.