on Aging and Life Shortening in Human Populations 491 Table If. Aging criteria tested. (Combined exposed and unexposed groups) Criterion Aging effect Correlation with age Marshallese ABCCstudies [8] Lymphocytes, peripheral blood decrease Lymphocytes transformation' decrease 0.9 Greying of hair increase 0.8 Arcus senilis increase 0.8 ¥-globulins? Skin elasticity Skin looseness increase decrease increase 0.7 0.7 0.7 0.6 Visual acuteness decrease 0.7 0.4 Hearing Handgrip strength decrease decrease 0.7 0.6 0.6 0.3 Neuromuscular reaction? decrease 0.6 Diastolic blood pressure increase Cholesterol Whole body potassium?! Heart size ; increase decrease increase Systolic blood pressure increase 0.9 0.7 0.5 0.5 0.5 ; 0.4 0.4 0.4 0.2 0.3 1 Response of lymphocytes in culture to phytchemagglutinin stimulation. 2 Exposed individuals showed a difference and are not included. See section on immunohematological changes. 3 Light extinction test. 4 y spectrographic analysis. Represents lean body mass. Measurement of Aging Changes I would like now to briefly describe some empirical studies that have been carried out in irradiated populations in an attempt to measure aging and see if there was any correlation with radiation exposure. Though the in- juriouseffect of irradiation in producing aging-like effects no doubt occursat the time of irradiation, the expression of such injury may not be evident until years later. Since aging changes are poorly understood andtherefore,difficult to measure, several investigations by the ABCC [17-19] and in the Mar- shallese (7, 8, 11] have been conductedto detect aging effects of irradiation by comparison of measurements of recognizable senile changes in age-matched cohorts of exposed and suitable unexposed comparison populations. Many of these changes could be measureddirectly, others had to be subjectively assessed on a 1-4-++ basis. In table II are listed some of these criteria used in de- werniyT 7 creasing order of their statistical correlation with chronological age. Al- - oy “y ™) 5 UL? b 23 - al +