Metabolic Syndrome and Breast Cancer Risk in the Study of Osteoporotic Fractures

Components of metabolic syndrome are linked to increased breast cancer risk, but no study has examined associations between metabolic syndrome as a single entity and breast cancer incidence. We evaluated the effect of the number of metabolic syndrome components on breast cancer risk.

Data were from the Study of Osteoporotic Fractures, a prospective cohort of women over age 65 (N=8,956). Metabolic syndrome components evaluated at baseline were: elevated waist circumference, hypertension, and diabetes. Incident breast cancers were confirmed by pathology report. We compared women with 0, 1, and 2-3 metabolic syndrome components. We used Cox proportional hazards regression to calculate associations for all breast cancer and separately for estrogen receptor (ER)+ and progesterone receptor (PR)+ cases.

At baseline, 28.8% had 2-3 components of metabolic syndrome. A total of 551 breast cancer cases were identified over an average follow-up of 14.4 years. Women with 2-3 components had increased breast cancer risk compared to those with no components (HR 1.30, 95% CI 1.01-1.68) adjusting for age, hormone use, and family history of breast cancer. Risk of ER+ (HR 1.51, 95% CI 1.11-2.04) and PR+ (HR 1.54, 95% CI 1.10-2.16) cancer was elevated for women with 2-3 components. These results became attenuated and not statistically significant when adjusted for body mass index.

Metabolic syndrome may be on a causal pathway linking obesity to increased postmenopausal breast cancer risk. Managing components of metabolic syndrome might offer an approach for breast cancer prevention.

Student's role: My role in this project was conducting all statistical analysis and creating all figures and data tables. In addition, I wrote the abstract and statistical methods section for the final manuscript.