title: Exercise is associated with reduced risk for incident dementia among persons 65 years of age and older.
abstract: BACKGROUND
  Alzheimer disease and other dementing disorders are major sources of morbidity and mortality in aging societies. Proven strategies to delay onset or reduce risk for dementing disorders would be greatly beneficial.
  
  
  OBJECTIVE
  To determine whether regular exercise is associated with a reduced risk for dementia and Alzheimer disease.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Group Health Cooperative, Seattle, Washington.
  
  
  METHODS
  1740 persons older than age 65 years without cognitive impairment who scored above the 25th percentile on the Cognitive Ability Screening Instrument (CASI) in the Adult Changes in Thought study and who were followed biennially to identify incident dementia.
  
  
  METHODS
  Baseline measurements, including exercise frequency, cognitive function, physical function, depression, health conditions, lifestyle characteristics, and other potential risk factors for dementia (for example, apolipoprotein E epsilon4); biennial assessment for dementia.
  
  
  RESULTS
  During a mean follow-up of 6.2 years (SD, 2.0), 158 participants developed dementia (107 developed Alzheimer disease). The incidence rate of dementia was 13.0 per 1000 person-years for participants who exercised 3 or more times per week compared with 19.7 per 1000 person-years for those who exercised fewer than 3 times per week. The age- and sex-adjusted hazard ratio of dementia was 0.62 (95% CI, 0.44 to 0.86; P = 0.004). The interaction between exercise and performance-based physical function was statistically significant (P = 0.013). The risk reduction associated with exercise was greater in those with lower performance levels. Similar results were observed in analyses restricted to participants with incident Alzheimer disease.
  
  
  CONCLUSIONS
  Exercise was measured by self-reported frequency. The study population had a relatively high proportion of regular exercisers at baseline.
  
  
  CONCLUSIONS
  These results suggest that regular exercise is associated with a delay in onset of dementia and Alzheimer disease, further supporting its value for elderly persons.
authors.affiliation: Center for Health Studies, Group Health Cooperative, Seattle, Washington 98101-1448, USA. larson.e@ghc.org
authors.forename: Eric B
authors.initials: EB
authors.lastname: Larson
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: James D
authors.initials: JD
authors.lastname: Bowen
authors.forename: Wayne C
authors.initials: WC
authors.lastname: McCormick
authors.forename: Linda
authors.initials: L
authors.lastname: Teri
authors.forename: Paul
authors.initials: P
authors.lastname: Crane
authors.forename: Walter
authors.initials: W
authors.lastname: Kukull
mesh_terms: D017668:Age of Onset; D000368:Aged; D000544:Alzheimer Disease / Q000453:epidemiology / Q000517:prevention & control; D015897:Comorbidity; D003704:Dementia / Q000453:epidemiology* / Q000517:prevention & control*; D015444:Exercise; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008019:Life Style; D011446:Prospective Studies; D012307:Risk Factors; D016019:Survival Analysis