Modelling the effects of exposure to whole-body vibration on low-back pain and its long-term consequences for sickness absence and associated work disability

BackgroundExposure to whole-body vibration (WBV) is a well-known risk factor for the occurrence of low-back pain (LBP). Little is known about the long-term course of back pain in workers exposed to WBV and the consequences for (temporary) disability, due to lack of cohort studies with sufficiently long follow-up periods.MethodsA systematic review of the literature was performed to assess associations between exposure to WBV and LBP, sickness absence due to low-back disorders and permanent disability. A meta-analysis was used to estimate the prevalences of LBP and sickness absence due to low-back disorders in occupational populations, depending on relevant exposure characteristics. These prevalences were converted into probabilities for transitions between no complaints, LBP, sickness due to LBP, and disability. A Markov model was applied to evaluate a hypothetical cohort of workers without LBP at the start of the cohort and a follow-up of 40 years (40 cycles of 1 year) to reflect a long-life career with continuous exposure to WBV.ResultsIn this hypothetical cohort it was estimated that among workers with the highest exposure to WBV on average about 47 weeks of their working life were lost due to sick leave because of LBP, which is approximately 2.5% of their working life. When all workers on prolonged sick leave for 52 weeks would remain disabled for the rest of their working life, a maximum of 23.4% of their working life could be lost due to high WBV exposure. Among workers without or low exposure to WBV the corresponding losses were 0.8% and 7.8%, respectively.ConclusionThe approach to assess years of work lost due to an occupational exposure may provide a more adequate description for stakeholders than the traditional measures of relative risk or attributable risk fraction. The concept of work years lost may also facilitate a better appreciation of the potential benefits of preventive measures.