title: Physical activity level and future risk of mild cognitive impairment or dementia: a critically appraised topic.
abstract: BACKGROUND
  The relationships between physical activity, cognition, and development of neurodegenerative diseases represent an area of intense research interest. Meta-analyses and prospective cohort studies show that greater levels of physical activity are associated with lower dementia risk. Most studies, however, depend on self-report data that are subject to recall and other biases. Obtaining objective and quantitative physical activity data could strengthen observational study validity.
  
  
  OBJECTIVE
  To examine the association between objectively measured daytime activity and mild cognitive impairment (MCI) or Alzheimer disease (AD).
  
  
  METHODS
  The objective was addressed through the development of a structured, critically appraised topic. We incorporated a clinical scenario, background information, a structured question, literature search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions. Participants included consultant and resident neurologists, clinical epidemiologists, a medical librarian, and behavioral neurology and neuropsychiatry content experts.
  
  
  RESULTS
  We selected a prospective, single-center cohort study of 716 cognitively normal elderly participants followed for 3.5 years. Greater levels of physical activity, as measured using wrist actigraphy, were associated with a lower risk of incident MCI or AD (hazard ratio, 0.477; 95% confidence interval, 0.273-0.832).
  
  
  CONCLUSIONS
  Objective measurement confirms that greater levels of physical activity are associated with decreased risk of a future diagnosis of MCI or AD. Further studies are needed to confirm the temporal association of exercise and future cognitive health and understand the relevant underlying biological mechanisms.
authors.affiliation: *Department of Neurology †Department of Library Services, Division of Education Administration ‡Department of Psychiatry, Mayo Clinic, Scottsdale, AZ and Phoenix, AZ.
authors.forename: Gretchen E
authors.initials: GE
authors.lastname: Schlosser Covell
authors.forename: Charlene R
authors.initials: CR
authors.lastname: Hoffman-Snyder
authors.forename: Kay E
authors.initials: KE
authors.lastname: Wellik
authors.forename: Bryan K
authors.initials: BK
authors.lastname: Woodruff
authors.forename: Yonas E
authors.initials: YE
authors.lastname: Geda
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Caselli
authors.forename: Bart M
authors.initials: BM
authors.lastname: Demaerschalk
authors.forename: Dean M
authors.initials: DM
authors.lastname: Wingerchuk
mesh_terms: D060825:Cognitive Dysfunction / Q000453:epidemiology*; D003704:Dementia / Q000453:epidemiology*; D006801:Humans; D009043:Motor Activity; D012307:Risk Factors