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Life Span Study Report 6

Technical Report No. 10-71
JNIH-ABCC Life Span Study Report 6. Mortality among A-bomb survivors, 1950-70

Jablon S, Kato H
Editor's note: The following journal articles, based on this ABCC technical report, were published in the scientific literature:
  • Jablon S, Kato H: Studies of the mortality of A-bomb survivors. 5. Radiation dose and mortality, 1950-1970. Radiat Res 50:649-98, 1972
  • Jablon S, Kato H: Studies of the mortality of A-bomb survivors. 5. Radiation dose and mortality, 1950-70. Hiroshima Igaku [J Hiroshima Med Assoc] 26:538-72, 1973 (in Japanese)
  • Summary
    The mortality experience during the period 1 October 1950-31 December 1970 of the JNIH-ABCC Life Span Study cohort (extended) is presented. Tabulations have been made for mortality from all causes and for 18 specific causes and groups of causes including trauma: all disease, all malignant neoplasms, leukemia, malignant neoplasms exclusive of leukemia, malignant neoplasms of the stomach, the entire gastrointestinal system, lung, respiratory system, breast, cervix and uterus, other malignant neoplasms, benign or unspecified neoplasms, all disease exclusive of neoplasms, tuberculosis, vascular lesions of the central nervous system, disease of the circulatory system, and all other disease.

    Tabulations have generally been done for Hiroshima and Nagasaki combined and for the cities separately; for the sexes combined and separately; for all ages combined; and separately for those who were at the time of the atomic bombs (ATB) in the age ranges 0-9 years, 10-19, 20-34, 35-49, and 50 or more. Every tabulation shows the data not only for the whole 20-year period of study but for four subintervals: 1950-1954, 1955-1959, 1960-1964, and 1965-1970.

    The approach has been to calculate, for each count of observed deaths shown, the number that would be expected at Japanese national death rates. For this purpose, the annual death rates published by the Division of Health and Welfare Statistics of the Ministry of Health and Welfare have been employed.

    Analysis with respect to radiation effects on mortality has been done primarily in terms of the estimated radiation dose in rad, using the sum of the individual estimates of neutron and gamma radiation dose. Some supplementary tabulations employ a so-called RBE dose, wherein the relative biological effectiveness of neutrons is counted as five times that of gamma radiation. No analysis in terms of distance from the hypocenter has been done.

    The analysis showed that the mortality experience of the Not-in-City (NIC) comparison group has been very favorable, but that the advantage derived largely from the small subgroup called the early entrants (those who entered the cities within 30 days after the bombings) and who have had unusually low mortality. For the late entrant (more than 30 days after the bombings) component of the NIC group, advantages in mortality experience over the low dose (under 10 rad) survivors disappeared by 1960, but the early entrants maintained low mortality rates throughout the 20-year period. An exception to this rule was mortality from malignant neoplasms excluding leukemia. Cancer mortality among the early entrants reached the same level as in the late entrants by 1960, and during the period 1960-1970 the NIC group had no advantage over low dose survivors with respect to cancer mortality.

    Mortality from disease was higher among the survivors who had large radiation doses than among those with small doses or those not in the cities. The excessive mortality was especially prominent for leukemia, where the radiation effect appeared to be present even among those estimated to have had 10-49 rad. Mortality from cancer apart from leukemia was also elevated in survivors with large radiation doses, but could be demonstrated with reliability only among those with doses exceeding 200 rad.

    There were minor elevations in observed mortality from other causes of death than neoplasms but, all in all, there is little evidence of radiation effect on other causes of death, including stroke, circulatory system disease, and tuberculosis. At this time, radiation effects on mortality appear to involve chiefly leukemia and other neoplasms, including those specified as benign, or unspecified as to malignancy.

    There were observed differences in radiation effects on specific cancers; notably mortality from cancer of the cervix and uterus and from cancer of the stomach appeared to be less influenced by radiation than other cancers. However, the differences in rates cannot be stated with certainty because of relatively large sampling variability.

    Those survivors who were children under 10 years of age ATB were more strongly affected than older persons. At the level of deaths from all disease, mortality ratios in the 200+ rad group decreased with increasing age ATB and the drop from ages 0-9 to ages 10-19 was especially sharp.

    The data are too sparse to support any very fine analysis of the shape of the dose-response curve, especially at low levels of dose. However, there is nothing in the data to refute the idea that the effects are a linear function of total dose.

    Leukemia rates in the high dose groups declined persistently during the 20-year period under study, but had not yet reached normal levels during the last subinterval, 1965-1970. The rates for other cancers, however, increased during the study period, and the subinterval 1965-1970 was characterized by an especially sharp rise. The latent period for radiation induction of cancers other than leukemia appears, therefore, to be around 20 years or more, under the conditions of irradiation experienced by the survivors.

    An RBE of neutrons, compared with gamma radiation, of about five fits the leukemia data well, but may be too low for other cancer. On the other hand, introduction of an RBE factor greater than unity introduces convex curvature into what are fairly linear dose response relationships when plotted against the simple total dose.

    The leukemogenic effect of radiation is by far the most striking when effects are considered in ratio terms, as a multiplying factor on the rate normally to be expected. However, if effects are considered in terms of differences, as a so-called "excess number of deaths attributable to radiation," then the effects for neoplasms other than leukemia (taking malignant, benign, and unspecified together) actually somewhat exceed the leukemia effects over the entire 20-year period in the 200+ rad group.
    Editor's note: The following components of this report contain data on communicable disease frequencies, allergies, malignancies, and many other symptoms that may be of interest from a public health standpoint.

    List of Tables

    The Life Span Study Cohort Extended

    1. Number of persons
    2. Number of person-years at risk 1950-1970
    3. T65 dose estimates in rad
    4. Distance from hypocenter, survivors with dose unknown
    5. RBE dose estimates in rem
    6. Deaths from all causes by T65 dose
    7. Deaths from trauma
    8. Deaths from all diseases
    9. Deaths from all malignant neoplasms
    10. Deaths from leukemia
    11. Deaths from malignant neoplasms except leukemia
    12. Deaths from malignant neoplasms of stomach
    13. Deaths from malignant neoplasms of digestive organs & peritoneum
    14. Deaths from malignant neoplasms of trachea, bronchus, & lung
    15. Deaths from malignant neoplasms of respiratory system
    16. Deaths from malignant neoplasms of female breast
    17. Deaths from malignant neoplasms of cervix & uterus
    18. Deaths from malignant neoplasms of other
    19. Deaths from benign or unspecified neoplasms
    20. Deaths from all diseases except neoplasms
    21. Deaths from tuberculosis
    22. Deaths from vascular lesions of central nervous system
    23. Deaths from diseases of circulatory system except CNS
    24. Deaths from other disease
    25. Deaths from leukemia by RBE dose
    26. Deaths from malignant neoplasms except leukemia by RBE dose
    27. Calculation of "excess" deaths attributable to radiation
    List of Figures
    1. Mortality Ratio--Deaths from all causes, dose unknown by time
    2. Mortality Ratio--Deaths from all diseases, 200+ rad by age
    3. Mortality Ratio--Deaths from leukemia, 200+ & 100-199 rad by time
    4. Mortality Ratio--Deaths from leukemia, 200+ & 100-199 rad by age
    5. Mortality Ratio--Deaths from malignant neoplasms except leukemia, 200+ & 100-199 rad by age
    6. Mortality Ratio--Deaths from malignant neoplasms of trachea, bronchus, & lung, 0-9 rad by time
    7. Mortality Ratio--Deaths from malignant neoplasms of female breast 50+ rad by age
    8. Relative risk, major groups of cause of death, 200+ vs 0-9 rad
    9. Relative risk, various tumors as cause of death, 200+ vs 0-9 rad
    10. Mortality Ratio--Deaths from leukemia by T65 dose
    11. Mortality Ratio--Deaths from malignant neoplasms except leukemia by T65 dose
    12. Mortality Ratio--Deaths from malignant neoplasms except leukemia, 200+ rad, by time & city
    13. Mortality Ratio--Deaths from leukemia by T65 dose & city
    14. Mortality Ratio--Deaths from leukemia by RBE dose & city
    15. Mortality Ratio--Deaths from malignant neoplasms except leukemia by T65 dose & city
    16. Mortality Ratio--Deaths from malignant neoplasms except leukemia by RBE dose & city
    17. "Excess" mortality deaths from malignant neoplasms, 200+ rad by time