EXPOSURE-RESPONSE RELATIONSHIP IN THE HAND-ARM VIBRATION SYNDROME - AN OVERVIEW OF CURRENT EPIDEMIOLOGY RESEARCH

The complex of vascular, neurologic, and osteoarticular disorders occu rring in the upper limbs of vibration-exposed workers is called hand-a rm vibration syndrome. There is epidemiologic evidence for an increase d occurrence of peripheral sensorineural disorders in occupational gro ups working with vibrating tools. An excess risk for wrist osteoarthro sis and for elbow arthrosis and osteophytosis has been reported in wor kers exposed to shocks and low-frequency vibration of high magnitude f rom percussive tools. However, there are too few epidemiology data to enable reliable conclusions to be drawn about exposure-response relati onships for both sensorineural disturbances and bone and joint disorde rs caused by hand-transmitted vibration. Cross-sectional and longitudi nal epidemiology studies have shown that occupational exposure to hand -transmitted vibration from a great variety of hand-held tools is sign ificantly associated with an increased occurrence of digital vasospast ic disorders called vibration-induced white finger (VWF). The proposal of an exposure-response relationship for VWF has been included in an annex to the international standard ISO 5349. The findings of several epidemiology studies have shown a poor agreement between the risk for VWF observed in various occupational groups and that predicted by the ISO 5349 model. Both overestimation and underestimation of the occurre nce of VWF have been reported by investigators. It has been argued tha t the current ISO frequency-weighting curve for hand-transmitted vibra tion may be inappropriate for the assessment of vibration-induced adve rse vascular effects. Alternative exposure-response relationships for VWF have been suggested in recent epidemiology studies. The epidemiolo gy data used to construct current exposure-response relationships for vibration-induced injuries are primarily derived from cross-sectional studies. Future epidemiology research should be based on prospective c ohort studies because the design characteristics of such studies permi t the study of cause-effect relationships and the formulation of etiol ogic hypotheses.