Observations on the healthy worker effect.

Follow-up mortality data from ten groups of employed persons are compared to the mortality rates of the United States general population. Comparisons related to the healthy worker effect (HWE) are computed. As measured by a relative comparison, the standardized mortality ratio (SMR), the HWE is seen to have a dynamic phase and a plateau phase in relation to length of follow-up. In contrast, the HWE as measured by an absolute comparison has little relationship to length of follow-up. Age at entrance into follow-up is strongly related to the absolute risk of mortality, but has little or no relation to the relative risk (SMR). Issues related to the evaluation and minimization of the healthy worker effect are discussed.