Diabetes, physical activity and breast cancer among Hispanic women

We assessed the association between diabetes and breast cancer and whether physical activity modified the effect of diabetes on breast cancer in Hispanic women.

We used data from a case-control study of breast cancer among Hispanic women aged 30-79 conducted between 2003 and 2008 on the Texas-Mexico border. In-person interviews were completed with 190 incident breast cancer cases ascertained through surgeons and oncologists, and 979 controls who were designated as both high-risk (n=511) and low-risk (N=468) for breast cancer (with respective response rates of 97%, 83% and 74%).

After adjustment for menopausal status and mammography screening, there was no effect of diabetes on breast cancer risk (high-risk control group odds ratio [OR] 1.02, 95% confidence interval [CI] 0.71-1.48; low-risk control group OR 0.87, 0.58-1.30). Women who had a diabetes history and did not exercise were at no risk of breast cancer (OR 0.96, 95% CI 0.63-1.48) or a slightly reduced breast cancer risk (low-risk control group OR 0.72, 95% CI 0.46-1.15) depending on the control group used, while women with diabetes who did exercise had significantly reduced breast cancer risk (OR 0.41, 95% CI 0.21-0.83) regardless of the control group used (high-risk control group p-value for interaction=0.013, low-risk control group p-value for interaction 0.183).

Should other studies confirm our results, physical activity should be explored as a means of reducing breast cancer risk in diabetic women.