title: Effects of physical activity on breast cancer prevention: a systematic review.
abstract: BACKGROUND
  Observational studies have reported an association between physical activity and breast cancer risk reduction. This study aims to evaluate the effect of physical activity on breast cancer prevention.
  
  
  METHODS
  Articles were identified through literature available on Electronic databases (PubMed, Embase, Scielo, Cochrane, CINAHL, Cancerlit, and Google Scholar) and manual searches. Case control and cohort studies were assessed for methodological quality, using the Newcastle-Ottawa scale.
  
  
  RESULTS
  Size, population, components, and characteristics of physical activity, and menopausal status were documented. Review Manager 5.1 performed analysis using the statistical method of Mantel-Haenszel. Fixed-effect analysis with dichotomous data, testing subgroups and calculating odds ratio with a confidence interval of 95% were used.
  
  
  RESULTS
  7 cohort studies and 14 case control studies were evaluated. Statistical evidence found that physical activity reduces the risk of breast cancer in case-control studies [OR = 0.84 (0.81-0.88)] (heterogeneity 72%) and cohort studies [OR = 0.61 (0.59-0.63)] (heterogeneity 100%).
  
  
  CONCLUSIONS
  Physical activity seems to prevent breast cancer mainly in postmenopausal women.
authors: Dept of Obstetrics and Gynecology, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil.
authors: Ana Katherine
authors: AK
authors: Gonçalves
authors: Gilzandra Lira
authors: GL
authors: Dantas Florencio
authors: Maria José
authors: MJ
authors: Maisonnette de Atayde Silva
authors: Ricardo Ney
authors: RN
authors: Cobucci
authors: Paulo César
authors: PC
authors: Giraldo
authors: Nancy Michelle
authors: NM
authors: Cote
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D016022:Case-Control Studies; D015331:Cohort Studies; D015444:Exercise; D005260:Female; D006801:Humans; D009043:Motor Activity; D012306:Risk; D040242:Risk Reduction Behavior