Cognitive Function Among Elderly Survivors Prenatally Exposed to Atomic Bombings

Abstract

BackgroundA cohort of children prenatally exposed to the 1945 atomic bombings in Japan revealed harmful effects of ionizing radiation in a variety of measures of cognitive function, including mental retardation. Here we examined cognitive function in the non-affected, now elderly, cohort. MethodsFrom 2011-2015, using the Cognitive Abilities Screening Instrument and a maternal uterine radiation dose estimated with the 2002 dosimetry system, we evaluated 303 prenatally exposed subjects and their non-exposed controls from the Adult Health Study of the Radiation Effects Research Foundation, excluding those who had shown marked cognitive effects earlier. About 11% of the subjects were exposed to more than 250 mGy. We examined a self-reported disease history and, using regression analysis, evaluated the relationship between cognitive function and radiation exposures, adjusting for demographic factors. ResultsNone of the subjects reported a history of dementia. We also did not find a significant radiation effect on cognitive function overall or in any gestational-week group. Education was associated with a significant effect, but educational level was not associated with radiation dose. ConclusionWe found no significant radiation effect on cognitive function among 65- to 70-year-old subjects who were prenatally exposed to the bombings and did not have marked childhood cognitive function deterioration. The limitations of this study include a small sample size and potential bias pertaining to non-participation in the Adult Health Study or refusal of Cognitive Abilities Screening Instrument evaluation. Further investigations using various endpoints in other populations prenatally exposed to radiation are warranted.