DOSE-RESPONSE RELATIONSHIPS BETWEEN WHOLE-BODY VIBRATION AND LUMBAR-DISK DISEASE - A FIELD-STUDY ON 388 DRIVERS OF DIFFERENT VEHICLES

In a longitudinal study, the dose-response relationships between long term occupational exposure to whole-body vibration and degenerative pr ocesses in the lumbar spine caused by the lumbar disks were examined. From 1990 to 1992, 388 vibration-exposed workers from different drivin g jobs were examined medically and by lumbar X-ray. For each individua l, a history of all exposure conditions was recorded, and a cumulative vibration dose was calculated allowing comparisons between groups of low, middle, and high intensity of exposure. 310 subjects were selecte d for a follow-up four years later, of whom 90.6% (n = 281) agreed to participate. In comparing the exposure groups, the results indicate th at the limit value of a(zw(8h)) = 0.8 m/s(2) should be reviewed. The b est fit between the lifelong vibration dose and the occurence of a lum bar syndrome was obtained by applying a daily reference exposure of a( zw(8h)) = 0.6 m/s(2) as a limit value. The results became more distinc t still when only those subjects were included in the statistical anal ysis who had had no lumbar symptoms up to the end of the first year of exposure. The prevalence of lumbar syndrome is 1.55 times higher in t he highly exposed group when compared to the reference group with low exposure (CI95%=1.24/1.95). Calculating the cumulative incidence of ne w cases of lumbar syndrome in the follow-up period yields a relative r isk of RRMH = 1.37 (CI95% = 0.86/2.17) for the highly exposed group. I t is concluded that the limit value for the calculation of an individu al lifelong vibration dose should be based on a daily reference exposu re of a(zw(8h)) = 0.6 m/s(2). With increasing dose it is more and more probable that cases of lumbar syndrome are caused by exposure to vibr ation. (C) 1998 Academic Press.