Longitudinal changes in red blood cell distribution width decades after radiation exposure in atomic‐bomb survivors

Red blood cell distribution width (RDW), which generally increases with age, is a risk marker for morbidity and mortality in various diseases. We investigated the association between elevated RDW and prior radiation exposure by examining longitudinal RDW changes in 4204 atomic‐bomb survivors over 15 years. A positive association was found between RDW and radiation dose, wherein RDW increased by 0·18%/Gy. This radiation‐associated effect increased as the participants aged. Elevated RDW was also associated with higher all‐cause mortality. The biological mechanisms underlying these observed associations merit further investigation.