Dose-response relationship for lifetime excess mortality and temporal pattern of manifestation in mice irradiated neonatally with gamma rays.

The dose-response relationships for the lifetime excess mortality and temporal distribution of excess mortality were analysed using a data set from an experiment on the long-term effects of gamma irradiation in neonatal mice. The excess mortality was calculated based on an assumption that any increase in the mortality rate was attributable to radiation exposure. The dose-response relationship for the lifetime excess mortality was convex upward, whereas the shortening of the mean life span was proportional to the dose. The excess mortality at 1 Gy was estimated to be 35.6%. The relative risk decreased markedly with increasing age. However, the mortality rate in the irradiated group was persistently higher than the background rate of death, and the absolute risk increased with age. A logistic specification was used to analyze the temporal distribution of the excess mortality. The results of the analysis indicated a dose-dependent shortening of the latent period and a broadening of the distribution.