METHODS FOR INVESTIGATING AGE-DIFFERENCES IN THE EFFECTS OF PROLONGEDEXPOSURES

People experience physiological changes with age which;may lead to cha nges in sensitivity to many kinds of exposure. In situations of prolon ged, low level exposure, differences in the effects of exposures recei ved at different ages may be difficult to evaluate, since study member s receive low level exposures over a range of ages. Such investigation s require examination of the effects of different age-patterns of? exp osure. Three approaches to investigating age-related variability in th e effects of prolonged exposures are described: subcohort analyses; th e use of smooth weighting functions; and, the evaluation of separate e ffects of cumulative exposures received at different age ranges. Each method can contribute to the overall evaluation of age-specific exposu re effects. These methods are illustrated with occupational cohort dat a for employees of Oak Ridge National Laboratory. The methods presente d in this paper should facilitate examination of the effects of aging on sensitivity to prolonged exposures. (C) 1998 Wiley-Liss, Inc.