Incidence of Diabetes in the Atomic Bomb Survivors: 1969-2015

Context Recent epidemiological studies have shown increased risk of diabetes among childhood cancer survivors who received high therapeutic doses of radiation, particularly to the total body or to the abdomen. However, the effect of low-to-moderate dose radiation (<4 Gy) on the risk of diabetes is still unknown. Objectives To investigate the radiation effect on diabetes incidence among atomic bomb (A-bomb) survivors, and whether the dose response is modified by other factors including city, sex, and age at time of bombing (ATB). Methods 9131 participants without diabetes at baseline were observed through biennial clinical exams from 1969 to 2015. A Cox proportional hazards model was used to estimate hazard ratios (HR) to evaluate the dose response for diabetes incidence. Results During the study period, 1417 incident diabetes cases were identified. The overall crude incidence rate was 7.01/103 person-years. Radiation dose was significantly associated with diabetes incidence, with effect modification by city and age ATB. In Hiroshima, at ages 10 and 30 ATB, the HRs at 1 Gy of pancreatic radiation dose were 1.47 (95% CI, 1.31-1.66) and 1.13 (95% CI, 0.97-1.31), respectively. However, no significant radiation dose response was observed at these ages in Nagasaki. The HR for radiation dose was higher among those who were younger ATB and decreased 1% for each additional year of age. Conclusions Among A-bomb survivors, a radiation association was suggested for incidence of diabetes. Results were inconsistent by city and age ATB, which could indicate potential confounding of the radiation association with diabetes.