46 second degree in age was used when there was a significant departure from linearity. The criteria vibratory sense, handgrip,light extinction time, hand-tally count, and body potassium showed significant sex differences, and were therefore scaled for each sex (0 to 100%). An attemptto correlate a combined “physio- logic” age score with chronological age was done by obtaining a weighted average score for combined criteria for each age group (see Table 22). The absolute values ofthe correlation coefficients were used as the weighting factor. This has intuitive appeal, since the influenceon the final combined score of any particular aging criterion is propor- tional to the absolutevalue ofits correlation with age. Results of Aging Studies The results of these tests are presented graph- wa ically in Figures 34 to 48 and in Table 22. The mean values for each decadestarting at age 20 are plotted at the midpoint of that decade for exposed and unexposed groups separately and com- bined, along with the standarderrors of the means. The numberbeside each point is the numberof people tested. The curve or straight line (which- fects, in comparing exposed and unexposed groups, is not significant at the 5% level for any of the criteria. The over-all 7% increase in aging effects in the exposed group is notsignificant (= 0.27). In Figure 48 the composite weighted biological or physiologic age scores are plotted against chrono- logical age (means per decade). Combined mean values for exposed and unexposed groupsare also presented with standarderrors of the means. The over-all correlation of the biological age scores with chronological age is very good. The biological “age curve” (Figure 48) showsthat thereis less change in the younger age groups than thereis after about age 40. Mean values for exposed and unexposed are notsignificantly different. Discussion of Aging Studies Thoughthe criteria presented in this report show changes which are definitely correlated with chronological age on a group basis, such correlation is much less accurate on an individualbasis. These tests of aging are least useful in the younger age groups (20 to 40 years of age), since most of the criteria either are not present until later or if present showslight increase during this age period. ever best represents the particular data) is drawn and its equation presented. Thecoefficientof correlation with age andsignificanceis also presented. Most of the criteria show good correlation with Therefore, moresensitive tests are needed to show aging in these groups. Effects of radiation on aging as measured by these parameters were not detected in this population. Perhapsthe tests were not sensitive enough neuromuscular function, and skin retraction. posure sustained. It is not known if any of the “aging parameters” ordinarily associated with senescence are necessarily associated with irradiation aging, since the latter is very poorly defined aging. It is apparent that mostofthe criteria show the least change with age in the younger age groups, from 20 to 40 years of age, particularly systolic blood pressure, hearing, visual acuity, Above about 40 years of age the criteria show the greatest change. With a few criteria, changes in the older age grouptendtolevel off or be less steep (accommodation, visual acuity, skin looseness, and cholesterol). In Table 22 age and radiation dependence of these criteria are presented. The criteria are ar- ranged in descendingorderof correlation with aging as shown bythecorrelation coefficients. For those criteria in which sex differences were apparent, the 7 values for the two sexes were averagedto determinethe over-all correlation with aging. Though there wereisolated significant differences between the exposed and unexposed age groups for some criteria, no meaningful pattern emerged. The table showsthat the correlation with radiation ef- to detect such effects at the level of radiation ex- or understood. Even if they were, this would not necessarily meanthatthey are related to mortality, which is a morepertinent correlation. Suchcriteria as hair graying, arcus senilis, neuromuscular function, etc., would not seem to have any obvious relation to mortality. On the other hand, loss of vigor and organ disfunction could well predispose to the developmentofold age diseases which would enhance mortality. Increase in mortality andlife shortening in the exposed Marshallese is difficult to assay in view of the small numbers of people in- volved and theslightly greater proportion of older people originally in the exposed group compared with the unexposed group. Oneradiation effect which might beclassified underagingis the inducementof malignant disease