Age-at-exposure effects on risk estimates for non-cancer mortality in the Japanese atomicbomb survivors

Abstract

Statistically significant increases in non-cancer disease mortality with radiation dose havebeen observed among survivors of the atomic bombings of Hiroshima and Nagasaki. Theincreasing trends arise particularly for diseases of the circulatory, digestive, andrespiratory systems. Rates for survivors exposed to a dose of 1 Sv are elevatedby about 10%, a smaller relative increase than that for cancer. The aetiologyof this increased risk is not yet understood. Neither animal nor human studieshave found clear evidence for excess non-cancer mortality at the lower range ofdoses received by A-bomb survivors. In this paper, we examine the age and timepatterns of excess risks in the A-bomb survivors. The results suggest that the excessrelative risk of non-cancer disease mortality might be highest for exposure at ages30–49 years, and that those exposed at ages 0–29 years might have a very low excessrelative risk compared with those exposed at older ages. The differences in excessrelative risk for different age-at-exposure groups imply that the dose responserelationships for non-cancer disease mortality need to be modelled with adjustment forage-at-exposure.