Background: Late effects of radiation exposure to the atomic bomb have been evaluated including the Life Span Study (LSS).
Methods: Initial 120,321 people identified in 1950 were followed up until the end of 2003 using population registry system and death certificates. Among them, 86,611 subjects with known individual doses by the Dosimetry System 2002 (DS02) were analyzed. Excess relative risks per Gy of target organ dose (ERR/Gy) and their 95% confidence intervals were calculated by a Poisson regression model.
Results: Total of 50,620 subjects (58%) died during the follow up period. ERR/Gy in a linear model was 0.22 (95%CI: 0.18, 0.26) for all causes of death, and 0.47 (0.38, 0.56) for total solid cancer, 2.62 (0.47, 7.25) for urinary tract cancer, 1.60 (0.99, 2.37) for breast cancer, 1.12 (0.33, 2.26) for bladder cancer, and significantly increased for cancers of esophagus, stomach, colon, liver, gall bladder, lung, and ovary. Also, significantly increased for total leukemia (ERR/Gy: 4.3, 95%CI: 3.1, 5.8), but not for malignant lymphoma and multiple myeloma. ERR/Gy for total circulatory diseases (0.11, 95%CI: 0.05, 0.17) including heart diseases and stroke and respiratory diseases (0.21; 0.10, 0.33) significantly increased. Effect modification in ERR for solid cancer by sex, age at exposure, and attained age was significant.
Conclusions: Risk of death of total death, major cancers, and major chronic diseases significantly increased with dose-response to radiation in the LSS subjects throughout life. The risk of leukemia continues, albeit at a lower level than previously. The risk of stroke and heart diseases also increases at moderate-to-high doses. Those relative risks were larger in females and in those who were exposed at young age and getting smaller along with subjects’ age. The results of this study, six-year elongation of the study period, are consistent with the previous report.