Abstract
Estimates of the somatic risk of radiation exposure have mainly been based on the incidence of fatal cancers. An improvement on the estimates of the risk will be made by taking mean ages at deaths into consideration in addition to the incidence of cancer. The authors report on an index of contribution of each cause of death to life shortening. The index is the sum of three terms. The first term indicates a contribution of change in incidence and the second term indicates that of changes in mean age at death from the cause of death in question. The last term is an interaction term of the two factors mentioned above. If a radiation exposure increases incidence of a cause of death and shortens the mean age at death from the cause of death, the index gives a large positive value. On the other hand, an increase in incidence of a late occurring cause of death will bring about a small positive or sometimes negative value for the index. The index proposed here will be promising in estimating risks by ionizing radiation.
