Postmenopausal breast cancer in Iran; risk factors and their population attributable fractions

Abstract

Abstract Background Causes of the rapidly increasing incidence of breast cancer in Middle East and Asian countries are incompletely understood. We evaluated risk factors for postmenopausal breast cancer and estimated their attributable fraction in Iran. Methods We performed a hospital-based case–control study, including 493 women, diagnosed with breast cancer at 50 years or later between 2005–2008, and 493 controls. We used logistic regression models to estimate multivariable odds ratios (OR) and 95% confidence intervals (CI), and population attributable fractions (PAF) for significant risk factors. Results The risk of breast cancer decreased with increasing parity. Compared with nulliparous women, the adjusted OR (95% CI) was 0.53 (0.25-1.15) for parity 1–3, 0.47 (0.29-0.93) for parity 4–6 and 0.23 (0.11-0.50) for parity ≥7. The estimated PAF for parity (25) was approximately 25%. The family history was significantly associated with increased breast cancer risk, but not increasing height, early age at menarche, late age at first birth or short breastfeeding. Conclusions Decreasing parity and increasing obesity are determinants of increasing breast cancer incidence among Iranian women. These trends predict a continuing upward trend of postmenopausal breast cancer.

Keywords

• Breast neoplasm
• Postmenopausal
• Middle East
• Risk factor
• Attributable fraction