46 second degree in age was used when there was a significant departure from linearity. The criteria vibratory sense, hand grip, light extinction time, hand-tally count, and body potassium showed significant sex differences, and were therefore scaled for each sex (0 to 100% ). An attempt to correlate a combined “physiologic” 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 of the correlation coefficients were used as the weighting factor. This has intuitive appeal, since the influence on the final combined score of any particular aging criterion is propor- tional to the absolute value of its correlation with age. Results of Aging Studies The results of these tests are presented graphically in Figures 34 to 48 and in Table 22. The mean values for each decade starting at age 20 are plotted at the midpoint of that decade for exposed and unexposed groups separately and combined, along with the standarderrors of the means. The number beside cach point is the number of people tested, The curve or straight line (which- ever best represents the particular data) is drav in and its equation presented. The coefficient of cor- relation with ave and significance ts also resented. Most of the criteria show good correiation with aging. It is apparent that most ot the criteria show the least change with age in the vounger age groups, from 20 to 40 years of age, particularly systolic blood pressurc, hearing, visual acuity, neuromuscular function, and skin retraction. Above about 40 years of age the criteria showthe greatest change. With a few criteria, changes in 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 not significant (p=0.27) In Figure 48 the composite weighted biological or physiologic agescores are plotted against chronological 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) shows that there is less change in the younger age groups than thereis after about age 40. Mean values for exposed and unexposed are not significantly different. Discussion of Aging Studies Though the criteria presented in this report show changes whicnare definitely correlated with chronologi. a! age on a group basis, such correlation is muct less accurate on an individual basis These tests of aging are least useful in the younger age groups (20 to 40 vears of age), since most o! the criteria either are not present until later or if present showslight increase during this age period Therefore, more sensitive tests are needed ta show aving in these groups. Effects of radiation on aging as measured by these parameters were not detected in this popula- uon. Perhaps the tests were not sensitive enough to detect such effects at the level of radiation evposure 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 the older age group tend to level off or be less steep or understood. Even if they were, this would not necessarily mean that theyare related to mortality. which is a more pertinent correlation. Such criteria (accommodation, visual acuity, skin looseness, and as hair graving, arcus senilis, neuromuscular cholesterol). In Table 22 age and radiation dependence of these criteria are presented. The criteria are arranged in descending order of correlation with aging as shown by the correlation coefficients. For those criteria in which sex diflerences were apparent, the 7s valttes tor the two sexes were averaged to determine the over-all correlation with aging. Though there were isolated significant differences between the exposed and unexposed age groups for some function, etc., would not seem to have any obvious relation to mortalitv. On the other hand, loss of vigor and organ disfunction could well predispose to the development of old age diseases which would enhance mortality. Increase in mortality and life shortening in the exposed Marshallese ts difficult to assay in viewof the small numbers of people in- volved and the slightly greater proportion of older criteria, no meaningful pattern emerged. The people originally in the exposed group compared with the unexposed group. One radiation effect which might be classihed table shows that the correlation with radiation ef- underaging 1s the inducement of malignant discase