title: A meta-analysis of prospective studies on the role of physical activity and the prevention of Alzheimer's disease in older adults.
abstract: BACKGROUND
  The incidence of Alzheimer's disease is increasing as the global population ages. Given the limited success of pharmaceuticals in preventing this disease, a greater emphasis on non-pharmaceutical approaches is needed. The aim of this study was to quantify the association between Alzheimer's disease and physical activity in older adults over the age of 65 years.
  
  
  METHODS
  A meta-analytic approach was used to determine if physical activity reduced the risk of Alzheimer's disease in individuals 65 years or older. Some evidence indicates that physical activity may improve cognitive function in older adults, while other evidence is inconclusive. The purpose of this study was to examine if prevention of Alzheimer's disease is possible if started at a later age. The precise brain changes that occur with the onset of Alzheimer's disease are not fully known, and therefore may still be influenced by preventative measures even in advancing age. Determining if physical activity can inhibit the onset of the disease at any age may motivate individuals to adopt an "it's never too late" mentality on preventing the onset of this debilitating disease. Longitudinal studies of participants who were 65 years or older at baseline were included. A total of 20,326 participants from nine studies were included in this analysis.
  
  
  RESULTS
  The fixed effects risk ratio is estimated as 0.61 (95% CI 0.52-0.73) corresponding to a statistically significant overall reduction in risk of Alzheimer's disease in physically active older adults compared to their non-active counterparts.
  
  
  CONCLUSIONS
  Physical activity was associated with a reduced risk of Alzheimer's disease in adults over the age of 65 years. Given the limited treatment options, greater emphasis should be paid to primary prevention through physical activity amongst individuals at high-risk of Alzheimer's disease, such as those with strong genetic and family history.
authors.affiliation: School of Kinesiology and Health Science, York University, Room 364 Strong College, 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada. mwtb@yorku.ca.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Beckett
authors.affiliation: School of Kinesiology and Health Science, York University, Room 344 Norman Bethune College, 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada. cardern@yorku.ca.
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Ardern
authors.affiliation: School of Kinesiology and Health Science, York University, Room 364 Norman Bethune College, 4700 Keele Street, Toronto, Ontario, M3J 1P3, Canada. mrtondi@yorku.ca.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Rotondi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000517:prevention & control* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D011446:Prospective Studies