The aim of this multi-centre case-control study is to investigate the dose-response relationship between occupational load on the spine and diagnosis of a lumbar disc herniation. 286 male and 278 female patients with lumbar disc herniation between 25 and 70 years of age were prospectively recruited in four study regions (Frankfurt am Main, Freiburg, Halle, Regensburg). Population control subjects (453 males and 448 females) were obtained from the regional population registers. In a structured computer-assisted personal interview, a complete occupational history was elicited, including every occupational period that lasted at least half a year. On the basis of job task-specific supplementary surveys performed by trained technical experts of the accident insurance institutions, the situational spinal load represented by the compression at the lower lumbar spine was assessed for materials handling and working situations with forward bending. The cumulative spinal load was calculated using 10 alternative dose models, varying the minimum exposure limits for disc compression and shift dose as well as the weighting of the lumbar disc compression in relation to the respective duration. Confounder selection was based on biologic plausibility and on the "change-in-estimate criterion". Odds
ratios (OR) and 95% confidence intervals (CI) were calculated separately for men and women using unconditional logistic regression analysis, adjusted for age, region, and unemployment as major life event (in males) and psychosocial strain at work (in females). The Akaike information criterion was used to measure the goodness of fit of the single dose models. The results of this case-control study reveal a statistically significant positive relationship between cumulative spinal load caused by occupational manual materials handling and German Spine Study EPILIFT- manual materials handling - lumbar disc herniation - dose-response relationship - Mainz-Dortmund Dose Model working postures with forward bending and lumbar disc herniation in men as well as in women. In women, a positive doseresponse relationship between ccupational exposure and lumbar disc herniation (OR for the highest exposure category=2.5; 95% confidence interval CI1.6-3.8) was found. In men, prolapse risks increase in line with increasing cumulative spinal load (OR for the second-highest exposure category=3.9; 95%-CI 2.6-6.0), but decrease in the highest exposure category (OR=1.4; 95%-CI 0.6-3.2); the latter result might be explained by healthy worker effect. The Mainz-Dortmund Dose Model (MDD) is not one of the most appropriate dose models for explaining the dose-response relationship, mainly because of the high threshold limits of the MDD. Over-proportional weighting of workload intensity in relation to the respective duration does not improve the goodness of fit of the model regarding the risk of disc herniation. According to this multi-centre case-control study, cumulative load on the intervertebral discs is related to lumbar disc herniation in both men and in women. Based on the study shown here, there is also an increased risk of disc herniation below the MDD thresholds (regarding compression caused by materials handling, forward bending of the trunk and shift dose).