A Study of Interactions Between Work Risk Factors and Work Related Musculoskeletal Disorders.

Work related musculoskeletal disorders (WMSDs) appear to have many causes including factors in the work environment and in the performance of work. Whilst recent attention has been focused upon physical and psychosocial work factors as major determinants of WMSDs, interactions between these work factors have not been researched. This study has investigated these interactions, with particular emphasis to the lower back. WMSDs in this thesis have been described by symptoms involving aches, pain and discomfort and the main outcome of the study was the lower back with attention also paid to the neck, shoulders and upper limbs. A cross-sectional epidemiological investigation was conducted to determine whether interaction between physical and psychosocial work risk factors increased the risk associated with low-back disorders and other WMSDs. The study population consisted of approximately 1400 male and female workers performing manual handling, delivery driving, repetitive work and sedentary work within BOC Gases. Individual workers were classified into one of four exposure groups that were defined by different combinations of low/high physical and psychosocial exposure to work risk factors. Exposure and outcome data were collected using a self-report questionnaire, comprising of previously validated exposure items for physical and psychosocial factors and outcome measures. Exposure biases were investigated in a field study using 12 workers. The estimates of risk showed that high exposure to physical and psychosocial work risk factors increased the risk associated with low-back disorders greater than the sum of the relative independent exposure effects, indicating an interaction effect. Interaction effects between physical and psychosocial work risk factors were also observed for the wrist/hands and a tentative interaction was observed for the shoulder region. An interaction effect was not observed for the neck region. Possible explanations for these observations are provided. Risk reduction strategies aimed at prevention of work related musculoskeletal disorders should address both physical and psychosocial work risk factors as they interact to magnify the risk for some of the musculoskeletal regions studied. Preventive strategies should not, therefore, only focus on physical factors. The greatest benefits are likely to be realised when both physical and psychosocial factors are addressed. The mechanisms explaining the observed interactions are explored using the current literature and a research model is proposed to provide a platform for further research regarding work related musculoskeletal disorders