The 'healthy worker effect' on morbidity rates.

Studies relating mortality and occupation are difficult to interpret because of the "healthy worker effect." That effect is primarily due to the fact that individuals entering the labor force are in reasonably good health. A similar phenomenon might be expected in a comparison of morbidity among members of an occupational group with that of the general population. A comparison of morbidity among different population and occupation groups is made possible through the Household Interview Survey (HIS) of the National Center for Health Statistics. Data from the HIS for the years 1969 through 1974 were combined to form a sample classified according to race, sex, age, occupation, and occurrence of various health conditions. Among subjects between 25 and 59 years of age, age-specific morbidity ratios and standardized morbidity ratios were computed for blue-collar and professional/managerial employees and for unemployed who were either seeking or not seeking employment. There appears to be a "healthy worker morbidity effect" for chronic, but not for acute, conditions just as there is for mortality. The healthy worker effect for chronic morbidity maintains itself and, in fact, appears to increase throughout the 35-year period of stable employment. The age-specific morbidity ratio may have considerable theoretical importance for evaluating the related mortality experience of employed populations.