Abstract
Background and Purpose: We examined whether exposure to atomic bomb radiation altered cognitive function and/or incidence of dementia among the Adult Health Study cohort, consisting of atomic bomb survivors exposed at 13 years of age or older in the 1945 atomic bombings and their controls.
Method: Study subjects were 2286 non-demented subjects, aged 60 years or older at 1992 baseline examination. A two-phase procedure, including cognitive function screening and neurological examination by a neurologist, was applied for identification of dementia cases. To estimate atomic radiation's effects on incidence rate of dementia, we applied Poisson regression analysis, with consideration paid to other potential risk factors. Information regarding history of radiotherapy among study subjects was obtained by hospital survey and questionnaire.
Result: A-bomb radiation had no effect on cognitive function among survivors exposed at 13 years of age or older. A total of 206 subjects developed dementia based on DSM IV criteria during the average sex years of follow-up. Incidence per 1,000 person-years was 16.3 in the less than 5 mGy group, 17.0 in the 5-499 mGy group, and 15.2 in the 500 mGy or more group. AD was the predominant type of dementia. Poisson regression analysis showed that the incidence rates of all dementia, or its subtypes, were not affected by radiation exposure from the atomic bombings, even after adjustment was made for potential risk factors. While 68 subjects had histories of radiotherapy before this incidence study, only two dementia cases were diagnosed among them.
Conclusion: No association was found between previous radiation exposure and cognitive impairment and/or development of dementia among atomic bomb survivors in this longitudinal study.
