title: Cardiorespiratory fitness and brain atrophy in early Alzheimer disease.
abstract: OBJECTIVE
  To examine the correlation of cardiorespiratory fitness with brain atrophy and cognition in early-stage Alzheimer disease (AD).
  
  
  BACKGROUND
  In normal aging physical fitness appears to mitigate functional and structural age-related brain changes. Whether this is observed in AD is not known.
  
  
  METHODS
  Subjects without dementia (n = 64) and subjects with early-stage AD (n = 57) had MRI and standard clinical and psychometric evaluations. Peak oxygen consumption (VO(2)(peak)), the standard measure of cardiorespiratory fitness, was assessed during a graded treadmill test. Normalized whole brain volume, a brain atrophy estimate, was determined by MRI. Pearson correlation and linear regression were used to assess fitness in relation to brain volume and cognitive performance.
  
  
  RESULTS
  Cardiorespiratory fitness (VO(2)(peak)) was modestly reduced in subjects with AD (34.7 [5.0] mL/kg/min) vs subjects without dementia (38.1 [6.3] mL/kg/min, p = 0.002). In early AD, VO(2)(peak) was associated with whole brain volume (beta = 0.35, p = 0.02) and white matter volume (beta = 0.35, p = 0.04) after controlling for age. Controlling for additional covariates of sex, dementia severity, physical activity, and physical frailty did not attenuate the relationships. VO(2)(peak) was associated with performance on delayed memory and digit symbol in early AD but not after controlling for age. In participants with no dementia, there was no relationship between fitness and brain atrophy. Fitness in participants with no dementia was associated with better global cognitive performance (r = 0.30, p = 0.02) and performance on Trailmaking A and B, Stroop, and delayed logical memory but not after controlling for age.
  
  
  CONCLUSIONS
  Increased cardiorespiratory fitness is associated with reduced brain atrophy in Alzheimer disease (AD). Cardiorespiratory fitness may moderate AD-related brain atrophy or a common underlying AD-related process may impact both brain atrophy and cardiorespiratory fitness.
authors.affiliation: Department of Neurology, Hoglund Brain Imaging Center, University of Kansas School of Medicine, 3599 Rainbow Blvd, MSN 2012, Kansas City, KS 66160, USA. jburns2@kumc.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Burns
authors.forename: B B
authors.initials: BB
authors.lastname: Cronk
authors.forename: H S
authors.initials: HS
authors.lastname: Anderson
authors.forename: J E
authors.initials: JE
authors.lastname: Donnelly
authors.forename: G P
authors.initials: GP
authors.lastname: Thomas
authors.forename: A
authors.initials: A
authors.lastname: Harsha
authors.forename: W M
authors.initials: WM
authors.lastname: Brooks
authors.forename: R H
authors.initials: RH
authors.lastname: Swerdlow
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology / Q000502:physiology; D000544:Alzheimer Disease / Q000473:pathology* / Q000503:physiopathology* / Q000523:psychology; D001284:Atrophy; D001921:Brain / Q000473:pathology* / Q000503:physiopathology*; D003071:Cognition / Q000502:physiology; D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D010809:Physical Fitness / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D013997:Time Factors