title: Radiation Effects on Cognitive Function Among Atomic Bomb Survivors Exposed at or After Adolescence.
abstract: The objective of this study was to investigate radiation effects on longitudinal pre-dementia cognitive decline among participants who developed dementia as well as on those who did not develop dementia during follow-up.
  
  
  
  Measuring cognitive function with the Cognitive Abilities Screening Instrument approximately every 2 years, we followed 1844 atomic bomb survivors participating in the Adult Health Study of the Radiation Effects Research Foundation from 1992 to 2011. Participants were adolescents or older when exposed to between 0 and 4 Gy. Approximately 15% and 40% of participants were exposed to ≥1 Gy and <5 mGy, respectively. At study start, participants were dementia-free and between 60 and 80 years old. Three-quarters of the participants returned after baseline, averaging 8.4 years of follow-up. During follow-up, 313 developed dementia. We used cognitive scores before dementia onset for analysis and a mixed-effects model to estimate radiation effects on longitudinal change of cognition, adjusting for dementia occurrence, age, sex, and education.
  
  
  
  Cognition level was significantly associated with age, education, and dementia occurrence but not with radiation dose or sex. Cognitive decline accelerated with increasing age, especially among participants who developed dementia. Neither radiation nor education was significantly associated with the degree of deterioration with age. Radiation did not modify the different cognitive decline by dementia occurrence.
  
  
  
  Radiation did not significantly affect cognition among atomic bomb survivors exposed at or after adolescence.
authors.affiliation: Departments of Clinical Studies and Statistics, Radiation Effects Research Foundation, Hiroshima, Japan. Electronic address: yamada@rerf.or.jp.
authors.forename: Michiko
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Departments of Clinical Studies and Statistics, Radiation Effects Research Foundation, Hiroshima, Japan.
authors.forename: Reid D
authors.initials: RD
authors.lastname: Landes
authors.affiliation: Department of Physical Therapy, Hiroshima International University, Higashi-Hiroshima, Japan.
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Mimori
authors.affiliation: Department of Clinical Neuroscience and Therapeutics, Hiroshima University, Hiroshima, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Nagano
authors.affiliation: Department of Nutritional Sciences, Yasuda Women's University, Hiroshima, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Sasaki
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D003071:Cognition / Q000528:radiation effects*; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D004522:Educational Status; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D054043:Nuclear Weapons; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000009:adverse effects*; D017741:Survivors; D055815:Young Adult
keywords: Aging; Cognition; Cohort study; Dementia; Education; Radiation