title: Brain pathology contributes to simultaneous change in physical frailty and cognition in old age.
abstract: OBJECTIVE
  First, we tested the hypothesis that the rate of change of physical frailty and cognitive function in older adults are correlated. Next, we examined if their rates of change are associated with the same brain pathologies.
  
  
  METHODS
  About 2,167 older adults participating in the Religious Orders Study and the Rush Memory and Aging Project had annual clinical evaluations. Bivariate random coefficient models were used to estimate simultaneously the rates of change in both frailty and cognition, and the correlation of change was characterized by a joint distribution of the random effects. Then, we examined whether postmortem indices from deceased were associated with the rate of change of frailty and cognition.
  
  
  RESULTS
  During an average follow-up of 6 years, frailty worsened by 0.09 unit/y and cognition declined by 0.08 unit/y. Most individuals showed worsening frailty and cognition (82.8%); 17% showed progressive frailty alone and <1% showed only cognitive decline. The rates of change of frailty and cognition were strongly correlated (ρ = -0.73, p < .001). Among deceased (N = 828), Alzheimer's disease pathology, macroinfarcts, and nigral neuronal loss showed independent associations with the rate of change in both frailty and cognition (all ps < .001). In these models, demographics explained about 9% of the variation in individual rate of change in frailty, and neuropathologies explained about 8%. In contrast, demographics and neuropathologies accounted for 2% and 30%, respectively, of the variance in the cognitive decline.
  
  
  CONCLUSIONS
  The rates of change in frailty and cognition are strongly correlated and this may be due in part because they share a common pathologic basis.
authors.affiliation: Rush Alzheimer's Disease Center, Department of Neurological Sciences, Aron_S_Buchman@rush.edu.
authors.forename: Aron S
authors.initials: AS
authors.lastname: Buchman
authors.affiliation: Rush Alzheimer's Disease Center, Department of Neurological Sciences.
authors.forename: Lei
authors.initials: L
authors.lastname: Yu
authors.affiliation: Rush Alzheimer's Disease Center, Behavioral Sciences, and.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Wilson
authors.affiliation: Rush Alzheimer's Disease Center, Behavioral Sciences, and.
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Boyle
authors.affiliation: Rush Alzheimer's Disease Center, Department of Neurological Sciences, Department of Pathology (Neuropathology), Rush University Medical Center, Chicago, Illinois.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Schneider
authors.affiliation: Rush Alzheimer's Disease Center, Department of Neurological Sciences.
authors.forename: David A
authors.initials: DA
authors.lastname: Bennett
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001921:Brain / Q000473:pathology*; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D016330:Frail Elderly; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009483:Neuropsychological Tests
keywords: Aging; Brain pathology.; Cognition; Physical frailty