Morbidity studies of workers exposed to whole body vibration.

Insurance claims for medical services submitted on behalf of a group of workers in the construction industry were collected over a 20-month period. The morbidity experience of those workers exposed to whole body vibration was contrasted with that of an unexposed control group eligible for benefits under the same plan. Using Mantel-Haenszel adjustment for age and experience, a significantly elevated relative risk was found among the exposed group in three of the thirty disease categories studied. In no disease category did the control group possess a significantly higher risk of requiring medical services. A striking proportion of the disease categories showed an initial increase in risk for exposed workers followed by a decrease with experience. This pattern suggests a selection process in which workers leave exposed-group jobs as they become afflicted with certain disease conditions.