A meta-analysis was undertaken using a random effects model to investigate the association between diabetes and breast cancer risk.
Thirty nine independent risk estimates were available from observational epidemiological studies. The Summary Relative Risk (SRR) for breast cancer in women with diabetes was 1.27 (95% Confidence Interval (CI), 1.16-1.39) with no evidence of publication bias. Prospective studies showed a lower risk (SRR 1.23 [95% CI, 1.12-1.35]) than retrospective studies (SRR 1.36 [95% CI, 1.13-1.63]). Type 1 diabetes, or diabetes in pre-menopausal women, were not associated with risk of breast cancer (SRR 1.00 [95% CI, 0.74-1.35] and SRR 0.86 [95% CI, 0.66-1.12] respectively). Studies adjusting for body mass index (BMI) showed lower estimates (SRR 1.16 [95% CI, 1.08-1.24]), as compared to those not adjusted (SRR 1.33 [95% CI, 1.18-1.51]).
Conclusions: The risk of breast cancer in women with type 2 diabetes is increased by 27% but not for women at pre-menopausal ages or with type 1 diabetes. BMI appears to be a potential confounder related to both diabetes and breast cancer.
- breast cancer
- body mass indexd