A-bomb data: detection of bias in the Life Span Study cohort.

By drawing a distinction between A-bomb survivors with and without bomb-related injuries, it was possible to see that instead of the Life Span Study (LSS) cohort being a normal, homogenous population, there were significant differences between survivors with and without multiple injuries, and that these differences occurred largely among survivors who were under 10 or over 50 years of age when exposed. There also was a concentration of A-bomb-related injuries among survivors who eventually developed leukemia. So it is possible that deaths before 1950 had left the LSS cohort permanently biased in favor of persons who had high levels of resistance to all (early and late) effects of radiation. It is also possible that the high proportion of leukemia cases among the deaths of A-bomb survivors from 1950 to 1970 were because the radiation caused an initial leukocytosis followed by loss of immunologic competence.