Radiation-related mortality among offspring of atomic bomb survivors: a half-century of follow-up.

Our objective was to examine whether parental exposure to atomic bomb radiation has led to increased cancer and/or noncancer mortality rates among the offspring. We studied 41,010 subjects born from May 1946 through December 1984 (i.e., conceived between 1 month and 38 years after the bombings) and surviving for at least 1 year. One or both parents were in Hiroshima or Nagasaki at the time of the bombings and childbirth. We analyzed mortality data from 1946 to 1999 using the Japanese family registry system by Cox regression model and examined the effects of paternal and maternal irradiation with adjustment for city, sex, year of birth and parental age at childbirth. During follow-up, 314 cancer deaths and 1,125 noncancer disease deaths occurred. The mean age of living subjects was 45.7 years. Median doses were 143 mSv for 12,722 exposed fathers and 132 mSv for 7,726 exposed mothers. Cancer and noncancer mortality rates were no higher for subjects with exposed parents (5+ mSv or unknown dose) than for reference subjects (0-4 mSv), and mortality did not increase with increasing dose. For subjects with both parents exposed, the adjusted hazard ratios were 1.16 [95% confidence interval (CI) 0.92-1.46] for noncancer and 0.96 (95% CI 0.59-1.55) for cancer. This was true of deaths occurring both before and after 20 years of age. However, because of uncertainty due to the small number of deaths and relatively young ages of subjects, we cannot rule out an increase in disease mortality at this time.