Diabetes mellitus and risk of breast cancer: A meta‐analysis

Diabetes mellitus has been associated with an increased risk of several types of cancers, but its relationship with breast cancer remains unclear. We conducted a meta-analysis of case-control and cohort studies to assess the evidence regarding the association between diabetes and risk of breast cancer. Studies were identified by searching MEDLINE (1966-February 2007) and the references of retrieved articles. We identified 20 studies (5 case-control and 15 cohort studies) that reported relative risk (RR) estimates (odds ratio, rate ratio/hazard ratio, or standardized incidence ratio) with 95% confidence intervals (CIs) for the relation between diabetes (largely Type II diabetes) and breast cancer incidence.…