Physical activity and breast cancer: a systematic review

Epidemiology. 2007 Jan;18(1):137-57. doi: 10.1097/01.ede.0000251167.75581.98.


Background: Many epidemiologic studies have found an association between physical activity and breast cancer risk, although this has not been a consistent finding.

Methods: Studies were identified through a systematic review of literature available on PubMed through February 2006. We included all cohort and case-control studies that assessed total or leisure time activities in relation to occurrence or mortality of breast cancer. The fully adjusted risk estimates and 95% confidence intervals for the highest versus lowest level of activity were documented for each study as well as evidence for a dose-response relationship. Methodologic quality was also assessed. Due to statistical and methodologic heterogeneity among studies, we did not carry out statistical pooling. To draw conclusions, we performed a best-evidence synthesis taking study quality into account.

Results: Nineteen cohort studies and 29 case-control studies were evaluated. There was strong evidence for an inverse association between physical activity and postmenopausal breast cancer with risk reductions ranging from 20% to 80%. For premenopausal breast cancer, however, the evidence was much weaker. For pre- and postmenopausal breast cancer combined, physical activity was associated with a modest (15-20%) decreased risk. Evidence for a dose-response relationship was observed in approximately half of the higher-quality studies that reported a decreased risk. A trend analysis indicated a 6% (95% confidence interval = 3% to 8%) decrease in breast cancer risk for each additional hour of physical activity per week assuming that the level of activity would be sustained.

Conclusions: There is evidence for an inverse association between physical activity and breast cancer risk. The evidence is stronger for postmenopausal breast cancer than for premenopausal breast cancer.

Publication types

  • Review
  • Systematic Review

MeSH terms

  • Breast Neoplasms / epidemiology*
  • Breast Neoplasms / etiology
  • Breast Neoplasms / prevention & control*
  • Case-Control Studies
  • Cohort Studies
  • Exercise*
  • Female
  • Humans
  • Motor Activity*
  • Risk