title: Physical Activity and Alzheimer Disease: A Protective Association.
abstract: OBJECTIVE
  To explore whether being physically active can decrease Alzheimer disease (AD) risk.
  
  
  METHODS
  We conducted a meta-analysis of prospective observational cohort studies reporting the association between physical activity (PA) and incident AD. Relevant articles were identified by title and abstract in the electronic databases PubMed, ScienceDirect, and Scopus using the keywords Alzheimer, Alzheimer disease, Alzheimer's, Alzheimer's disease, physical activity, sport, exercise, sedentary, fitness, and combinations thereof for articles published in any language up to February 15, 2016. Criteria for consideration included division of the study cohort by PA levels and sample size specification for each PA level group, quantification (number) of persons who had development of AD, and PA assessment during time off work (not just work time). We followed the MOOSE (Meta-analyses of Observational Studies in Epidemiology) recommendations and used the Newcastle-Ottawa scale for study quality assessment.
  
  
  RESULTS
  Ten high-quality studies were included in meta-analysis I (23,345 participants). Follow-up ranged from 3.9 to 31 years, and the participants' age ranged from 70 to 80 years. The pooled odds ratio for development of AD in participants who were more vs less physically active was 0.65 (95% CI, 0.56-0.74; P<.001; no publication bias [P=.24] but with heterogeneity among studies [I(2)=31.32%]). We could identify participants' adherence to international PA recommendations in 5 studies, which constituted meta-analysis II (10,615 participants). The pooled odds ratio for development of AD in participants who were active vs those who were inactive was 0.60 (95% CI, 0.51-0.71; P<.001; no publication bias [P=.34] and no heterogeneity [I(2)=5.63%]).
  
  
  CONCLUSIONS
  Although the limitations of self-reported PA data must be considered, regular PA performed by elderly people might play a certain protective role against AD.
authors: Research Institute of Hospital 12 de Octubre ('i+12'), Madrid, Spain; GIDFYS, Department of Health Sciences, European University Miguel de Cervantes, Valladolid, Spain.
authors: Alejandro
authors: A
authors: Santos-Lozano
authors: Research Institute of Hospital 12 de Octubre ('i+12'), Madrid, Spain; European University of Madrid, Madrid, Spain.
authors: Helios
authors: H
authors: Pareja-Galeano
authors: Research Institute of Hospital 12 de Octubre ('i+12'), Madrid, Spain. Electronic address: fabian.sanchis@uv.es.
authors: Fabian
authors: F
authors: Sanchis-Gomar
authors: Departamento de Fisiatría y Enfermería, Facultad de Ciencias de la Salud y del Deporte, GENUD (Growth, Exercise, Nutrition and Development) Research Group, Instituto Agroalimentario de Aragón -IA2- (Universidad de Zaragoza-CITA), Zaragoza, Spain.
authors: Miguel
authors: M
authors: Quindós-Rubial
authors: Research Institute of Hospital 12 de Octubre ('i+12'), Madrid, Spain.
authors: Carmen
authors: C
authors: Fiuza-Luces
authors: Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile, and Universidad Autónoma de Chile, Temuco, Chile.
authors: Carlos
authors: C
authors: Cristi-Montero
authors: 2E Science, Robbio, Pavia, Italy.
authors: Enzo
authors: E
authors: Emanuele
authors: Research Institute of Hospital 12 de Octubre ('i+12'), Madrid, Spain; Departamento de Fisiatría y Enfermería, Facultad de Ciencias de la Salud y del Deporte, GENUD (Growth, Exercise, Nutrition and Development) Research Group, Instituto Agroalimentario de Aragón -IA2- (Universidad de Zaragoza-CITA), Zaragoza, Spain; Instituto Investigación Sanitaria Aragón (IIS Aragón), Zaragoza, Spain, and Centro Investigación Biomédica en Red Fisiopatología de la Obesidad y Nutrición (CIBERObn), Madrid, Spain.
authors: Nuria
authors: N
authors: Garatachea
authors: Research Institute of Hospital 12 de Octubre ('i+12'), Madrid, Spain; European University of Madrid, Madrid, Spain.
authors: Alejandro
authors: A
authors: Lucia
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000517:prevention & control*; D015444:Exercise; D006801:Humans; D011446:Prospective Studies; D065840:Protective Factors; D040242:Risk Reduction Behavior