The meta-analysis of previous epidemiological studies referenced above was designed to investigate the association between diabetes and risk of breast cancer risk. The analysis included 39 independent risk estimates from population studies.
Overall, women with diabetes were found to have 1.27 times the risk of breast cancer as those without diabetes, based on combined analysis of all the studies used in the analysis. Prospective studies (in which women with diabetes were followed before being diagnosed with breast cancer) reported a lower risk (1.23 x) than retrospective studies (1.36 x)). Type 1 diabetes was not found to be associated with breast cancer risk. Nor was diabetes in premenopausal women. Studies adjusting for body mass index (BMI) reported lower risk estimates (1.16 x) than those studies that were not adjusted for BMI (1.33). The authors conclude that the risk of breast cancer in women with type 2 diabetes is increased by 27%, a figure that is reduced to 16% after adjusting for body weight.
Please see our article on breast cancer and type 2 diabetes for more information.