45 eachlight as it appeared. The total time necessary to extinguish all the lights was measured. This test involved both manual dexterity and mentalreaction time”? (see Figure 33). (4) Hand Strength. The spring tension of the hand grip was measured in kilograms with a Smedly hand dynamometer." The maximum squeezestrength in the dominant handin 3 tries was recorded. Correlation of Data. In orderto place all the data on a commonbasis for comparison and com- bination, the data were converted to a percentage basis for each criterion. In the case of the measured data, values associated with least aging were taken as 0% (sometimesthe highest reading, as with handstrength; sometimes the lowest, as with hearing loss), and conversely the values showing Miscellaneous Tests. (1) Body Potassium Levels (*°K). Since loss of muscle mass occurs with aging most aging were taken as 100%. The estimated cri- muscle mass, it has been shown that body levels of The data were examined on an individual basis as spectrographic analyses were carried out in the Marshallese in a lead-shielded structure. In this way ‘°K levels were obtained and presented as were madelargely by using meansfor each decade and total body potassium is closely related to potassium decrease with age.**'’* Whole-body K/kg body weight. The accuracy of these data could have been improved by obtaining more precise determinations of lean body mass, such as by measurement of body water.’* The valueslisted are averages of the 1961 and 1965 determinations. (2) Blood Serum Cholesterol Levels. These were ob- terla with values of 0, 1+,2+,3+,and4+ were presented as 0, 25, 50, 75, and 100%, respectively. well as on a population basis, and comparisons age group. Except whereindicated, the data used were collected during the 11- and 12-year surveys. An analysis of variance was used to determine differences amongthefactors of sex, age, and radiation levels.* These data were programmed and analyzed on a high speed digital computer.** For each criterion, the combined score over sex and radiation level was correlated with age. A curve of tained in 1957 on sera sent to the United States.** *Mr. Keith Thompson of Brookhaven National Laboratory *S.H. Stoelting Co., Chicago, Hi. **The analyses were done at the National Institutes of Health by Dr. J.H. Bragdon and Mr. J.C. Lauter. did the statistical analvses of these data. **The Control Data Corporation 6600, at Brookhaven Na- uonai Laboratory. Table 22 Correlation of Criteria With Age and Radiation Exposure Correlation with age (r value) Correlation with radiation Percent Grayness Arcussenilis 0.87 0.83 +17.0 0.0 Accommodation 0.81 —14.1 Skin retraction Skin looseness Vibratory sense (M + F} Visual acuity Hearingloss Handgrip (M + F) Reaction time (M + F)(light extinctiontest) Systolic blood pressure Potassium (M + F) Cholesterol Neuromuscular function (M + F) (handtally) Combined scoret *N.S. - notsignificant at 5%level. 0.74 0.70 0.70** 0.69 0.67 0.67** 0.64** 0.55 0.41** 0.39 0.36** 0.99 + 7.3 + 1.6 — 1.4(M), + 14.0 + 7.9 +13.8(M), — 2.0(M), —11.5 — 14.6(M), —17.2 + 3.2(M), + 7.0 **7 values for males and females averaged. Significance* ( p) N.S. (0.70) N.S. (1.00) N.S. (0.11) + 24.6(F) + 13.8(F) —10.5(F) + 10.6(F) +1.1(F) N.S. N.S. N.S. N.S. N.S. NS. N.S. N.S. N.S. N.S. N.S. (0.68) (0.82) (0.90, 0.20) (0.59) (0.40) (0.15, 0.18) (0.88, 0.55) (0.30) (0.17, 0.22) (0.05) (0.85, 0.95) N.S. (0,27) *Weighted accordingto r value.