A comparison of approaches to modeling the relationship between ergonomic exposures and upper extremity disorders

Abstract

Background For a study of upper extremity musculoskeletal disorders among automobile manufacturing workers, an ergonomic exposure index was constructed by summing ten psychophysical (interview) items. Here we explore the sensitivity of the exposure–response relationship to the formulation of that index. Methods Five alternative exposure indices were constructed: three a priori weighting schemes and two sets of weights derived from multivariate regression coefficients. In addition, structural equation modeling was performed with LISREL. Results The original index and a priori weighting schemes had similar associations with upper extremity disorders, adjusted for nonoccupational covariates. A reasonable model fit was achieved in LISREL after two modifications; the standardized solution showed that nonneutral postures were significantly related to upper extremity signs and symptoms. Conclusions In this large population, with adequate range of exposures, the exposure–response relationship appeared generally robust to the mathematical formulation of the exposure index. Among the available exposure variables, postural strain had the strongest association. Am. J. Ind. Med. 37:645–655, 2000. © 2000 Wiley‐Liss, Inc.

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