title: Aspirin use and breast cancer risk: a meta-analysis and meta-regression of observational studies from 2001 to 2005.
abstract: OBJECTIVE
  To examine the recent epidemiological studies on aspirin use and breast cancer risk published from 2001 to 2005 within a meta-analysis, to investigate reasons for heterogeneity between the individual studies and to analyse a dose-response-relationship considering frequency and duration of use.
  
  
  METHODS
  We systematically searched for cohort-studies and case-control-studies from 2001-2005, which evaluated the association between aspirin and breast cancer risk. We calculated a pooled estimate for the relative risk (RR) and investigated reasons for heterogeneity between the individual studies and analysed a dose-response-relationship using random effects mixed models.
  
  
  RESULTS
  We identified 10 studies which met the inclusion criteria. The combined estimate of the RR was 0.75 (95%CI: 0.64, 0.88) using the random effects model. Heterogeneity between the studies could not be explained by the covariates study-type and study-population. The combination of frequency and duration of aspirin use resulted in a significant dose-response-relationship between aspirin use and breast cancer risk. Each additional pillyear reduced the breast cancer risk to about 2%.
  
  
  CONCLUSIONS
  Our meta-analysis supports the current evidence that aspirin may reduce breast cancer risk. Moreover, a dose-response-relationship seems to exist. However, results have to be interpreted carefully, as exposure categories were defined very heterogeneously among the studies which weakens the validity of the pooled estimates.
authors.affiliation: Technical University of Berlin, Department of Technology and Management, Berlin, Germany. Sandra.mangiapane@tu-berlin.de
authors.forename: Sandra
authors.initials: S
authors.lastname: Mangiapane
authors.forename: Maria
authors.initials: M
authors.lastname: Blettner
authors.forename: Peter
authors.initials: P
authors.lastname: Schlattmann
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000627:therapeutic use*; D001241:Aspirin / Q000008:administration & dosage / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D018849:Controlled Clinical Trials as Topic; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D015233:Models, Statistical; D012044:Regression Analysis; D015203:Reproducibility of Results; D012306:Risk
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D001241:Aspirin