Risk factors and the effectiveness of back belts in the prevention of back pain amongst forklift drivers subject to whole body vibration exposure
Master Thesis
2000
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University of Cape Town
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Motivation: Back pain is a major cause of absenteeism, lost work time and increased compensation and medical costs amongst workers and has been estimated to cost $20 billion annually in the United States. Back pain has long been associated with the driving of forklifts, and is a complex area of occupational health and safety, having many risk factors leading to musculo-skeletal injury. The health effects in this occupational group in South Africa, could be affecting upwards of 90 000 forklift drivers, and has a great direct and indirect influence on people's health at work as well as productivity and the economy. Purpose: To characterise the problem of back pain amongst forklift drivers with a view to reducing the morbidity from back pain, by evaluating the effectiveness or the use of back belts. Aim: To identify risk factors associated with back pain amongst forklift drivers at Portnet (handling wharf side cargo) in two cohorts of forklift drivers one using back belts and one control group, and to evaluate the relationship between back pain, the occupational environment (i.e.: forklift driving) and other associated factors, in order to establish the effectiveness of back belts in decreasing the severity and prevalence of back pain amongst forklift drivers. Objectives: 1.) To describe demographic and other relevant back pain risk factors in the two cohorts and to identify any significant differences between them. 2.) To characterise the compliance and frequency of use of the back belts by the user group. 3.) To measure vibration experienced in typical driving activities in the study population in order to characterise whole-body vibration exposures of the study subjects. 4.) To ascertain opinions and beliefs regarding back belts amongst users. 5.) To analyse, characterise and determine if any significant differences exist between the two groups as to the prevalence and severity of back pain, and what factors are associated with increased risk of back pain. Specifically to identify whether (a.) The frequency and/or intensity of use of back belts are associated with reduced risk for back pain, when controlling for all other risk factors, and (b.) Whether other factors modify this relationship. Study Design: Cross Sectional Study Design Subjects: Drivers of 3, 4, 4.5 and 5 ton forklifts in the permanent employment of Portnet, Durban, from the Point, Maydon Wharf (back belt group) and Combi-Terminal (control group) areas. Main Outcome Measures: Onset of back pain after starting driving, prevalence of regular back pain (ever), point prevalence (pain today), 1 year prevalence, severity of back pain, duration of pain, and treatment/medication sought for back pain. Results: The majority of forklift drivers (89%) in the study suffer from chronic back pain that is of a constant severity, and is significantly linked to the driving activities. The back belt wearers were more likely to suffer from back pain then the non-users (92% vs 80%). However, the belt wearers reported less severe pain than the control group, which could indicate the presence of a placebo effect related to the belt use. The belt users were more likely to suffer from pain of a longer duration, with less fluctuation in severity than the controls, and therefore a more constant type of pain (44% vs 41 %). The majority of bell wearers expressed the belief that the belts helped to reduce the back pain (81%). However, more objective measures do not bear out this conclusion when prevalence and severity of pain are compared to the control group. Drivers with back pain were more likely to wear the back belts and compliance was reduced as the prevalence of pain was reduced. These results may have been confounded by variations in the whole-body vibration exposure in the various test areas, and the inability to characterise individual whole-body vibration exposures and dose-response relationships. Conclusion: The prevalence of back pain in this study was high, with most drivers suffering from pain in the lower back region (79%), which was characterised as constant or chronic pain experienced either during or shortly after driving. Whole-body vibration levels were high in all test areas (1.9 m/s⁻², 1.3 m/s⁻² and 1.1 m/s⁻² predicted), and consistently exceeded the EEC machinery directive standards of 0.5 m/s⁻². Compliance with the use of back belts amongst drivers was high (90%), with most drivers (76%) wearing the belts on a regular basis whilst driving. The evidence for the effectiveness of back belts as a control measure against whole-body vibration remains obscure, and other more tested controls such as engineering, administrative and training of drivers should be implemented to address the problem following a holistic approach.
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Joubert, D. 2000. Risk factors and the effectiveness of back belts in the prevention of back pain amongst forklift drivers subject to whole body vibration exposure. University of Cape Town.