title: Longitudinal verbal fluency in normal aging, preclinical, and prevalent Alzheimer's disease.
abstract: BACKGROUND
  Few longitudinal studies evaluate differences in patterns of change of category compared to letter fluency across the spectrum of cognitive impairment.
  
  
  METHODS
  We compared change in category (animal and supermarket) and letter (F, A, S) fluency among 239 participants in 3 groups: remained cognitively normal throughout follow-up (n = 96), developed Alzheimer's Disease (AD; preclinical AD, n = 21), and with AD at initial testing (prevalent AD, n = 122).
  
  
  RESULTS
  At baseline, prevalent and preclinical AD groups scored lower on animal than letter fluency. On all fluency measures, the prevalent AD declined faster than other groups (all P < .0001), and preclinical AD declined faster than unimpaired (all P <or= .02). Overall, animal fluency declined faster than letter fluency; animal fluency declined significantly faster than letter fluency among cognitively normal and prevalent AD participants.
  
  
  CONCLUSIONS
  Greater longitudinal declines in category compared to letter fluency are consistent with cross-sectional studies. Steeper declines on both fluency measures distinguish preclinical AD from cognitively unimpaired individuals.
authors.affiliation: Alzheimer Disease Research Center, and Department of Neurology, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Clark
authors.forename: Margaret
authors.initials: M
authors.lastname: Gatz
authors.forename: Ling
authors.initials: L
authors.lastname: Zheng
authors.forename: Yu-Ling
authors.initials: YL
authors.lastname: Chen
authors.forename: Carol
authors.initials: C
authors.lastname: McCleary
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Mack
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000453:epidemiology*; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology; D003937:Diagnosis, Differential; D018450:Disease Progression; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008568:Memory; D015999:Multivariate Analysis; D009483:Neuropsychological Tests; D015995:Prevalence; D012660:Semantics; D013064:Speech Disorders / Q000175:diagnosis* / Q000453:epidemiology*