title: Dynamics of brain structure and cognitive function in the Alzheimer's disease neuroimaging initiative.
abstract: BACKGROUND
  On average, cognition declines as people age, but improvement can also occur.
  
  
  OBJECTIVE
  To evaluate the dynamics of age-related changes in brain structure and cognitive function in patients with mild Alzheimer's disease (AD) and mild cognitive impairment (MCI) and in healthy control (HC) older adults.
  
  
  METHODS
  High-resolution 3-Tesla MRI and clinical data were obtained from the Alzheimer's Disease Neuroimaging Initiative in 187 subjects (a cohort aged 55-91 years; AD=43, MCI=84, HC=60). At 24 months, 151 people had clinical and 128 had MRI follow-up. Brain structure was assessed using the Medial Temporal Atrophy Scale (MTAS) and the Brain Atrophy and Lesion Index (BALI). Cognition was assessed using the Mini-Mental State Examination (MMSE) and the Alzheimer Disease Assessment Scale-cognitive subscale (ADAS-cog). Responsiveness was tested. Changes were analysed using a multistate dynamic model, adjusted for age, gender, ApoE4 genotype and vascular risk factors.
  
  
  RESULTS
  Over 2 years, decline in brain structure and cognition predominated, each showing detectable effect sizes (Cohen's d=0.33 for MTAS, 0.32 for BALI, 0.41 for MMSE, 0.38 for ADAS-cog; standard response mean=0.71, 0.69, 0.50 and 0.47, respectively). Structural improvement was observed (10.2% in BALI and 0.8% in MTAS), as was cognitive improvement (23.2% MMSE, 27.2% ADAS-cog). Most people (66.7%) whose BALI score improved also improved in either the MMSE or ADAS-cog. No patient with MCI whose MTAS or BALI improved converted to AD.
  
  
  CONCLUSIONS
  Despite average decline in brain structure, improvement was observed and related to cognition and MCI-AD conversion. Ageing-related brain changes reflect a dynamic process.
authors.affiliation: Biodiagnostics Atlantic, National Research Council Canada, Halifax, Canada.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Song
authors.forename: Arnold
authors.initials: A
authors.lastname: Mitnitski
authors.forename: Ningnannan
authors.initials: N
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Kenneth
authors.initials: K
authors.lastname: Rockwood
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000473:pathology* / Q000523:psychology*; D001284:Atrophy / Q000473:pathology; D001921:Brain / Q000473:pathology*; D060825:Cognitive Dysfunction / Q000473:pathology* / Q000523:psychology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000523:psychology; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging / Q000379:methods / Q000523:psychology*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011569:Psychiatric Status Rating Scales; D012307:Risk Factors