Association between breastfeeding and breast cancer risk: evidence from a meta-analysis

Quantification of the association between breastfeeding and breast cancer risk is still conflicting. Therefore, we conducted a meta-analysis to summarize the evidence from epidemiological studies of breastfeeding with the risk of breast cancer. Pertinent studies were identified by a search of PubMed between January 1, 2008 and July 31, 2014. The random-effect model was used. Sensitivity analysis, subgroups analysis, and publication bias were conducted. Twenty-four articles with 27 studies involving 13,907 breast cancer cases were included in this meta-analysis. Pooled results suggested that breastfeeding was inversely [corrected] associated with the risk of breast cancer. The summary relative risk (RR) of breast cancer for the ever compared with never categories of breastfeeding was 0.613 (95% confidence interval [CI], 0.442-0.850). An inverse association was also found for the longest compared with the shortest categories of breastfeeding with the risk of breast cancer (RR=0.471; 95% CI, 0.368-0.602). No evidence of publication bias was found. Findings from this meta-analysis suggest that breastfeeding, particularly a longer duration of breastfeeding, was inversely associated with risk of breast cancer.