title: Trajectories of cognitive function in dementia-free subjects: Radiation Effects Research Foundation Adult Health Study.
abstract: OBJECTIVE
  To investigate associations between age, sex, education, and birth cohort and global cognitive decline among a population that would most likely not progress to dementia.
  
  
  METHODS
  A total of 1538 dementia-free subjects aged 60 to 80years in 1992 were followed up through 2011 without dementia occurrence. We assessed cognitive function using the Cognitive Ability Screening Instrument (CASI). Using stepwise-like model selection procedure, we built mixed-effects models for initial cognition and longitudinal cognition.
  
  
  RESULTS
  Initial CASI scores for younger age and more years of formal education were higher than those for older and less education. Sex did not show a significant effect. In the longitudinal analysis, cognitive decline became more rapid with increasing age. Sex and education did not modify the degree of deterioration with age. CASI scores were higher for younger cohorts and men due to differences in education levels.
  
  
  CONCLUSIONS
  Among dementia-free subjects, age is an important predictor of cognitive function level and cognitive decline. Education level affects cognitive function level, but did not affect cognitive decline. The results have implications not only for elucidation of the aging process, but also for reference in dementia screening.
authors.affiliation: Departments of Clinical Studies and Statistics, Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima, 732-0815, 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, 5-2 Hijiyama Park, Minami-ku, Hiroshima, 732-0815, Japan. Electronic address: rdlandes@rerf.or.jp.
authors.forename: Reid D
authors.initials: RD
authors.lastname: Landes
authors.affiliation: Department of Physical Therapy, Hiroshima International University, 555-36 Gakuendai, Kurose, Higashi, Hiroshima, 739-2695, Japan. Electronic address: y-mimori@hs.hirokoku-u.ac.jp.
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Mimori
authors.affiliation: Department of Clinical Neuroscience and Therapeutics, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Hiroshima, 734-0037, Japan. Electronic address: yachtz@hiroshima-u.ac.jp.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Nagano
authors.affiliation: Department of Nutritional Sciences, Yasuda Women's University, 6-13-1, Yasuhigashi, Asaminami-ku, Hiroshima, 731-0153, Japan. Electronic address: sasaki-h@yasuda-u.ac.jp.
authors.forename: Hideo
authors.initials: H
authors.lastname: Sasaki
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000453:epidemiology / Q000503:physiopathology*; D004522:Educational Status; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged
keywords: Aging; Cognition; Cohort study; Education; Gender; Non-demented subjects