Role of Menopause and Early Menarche in Breast Cancer: A Meta-Analysis of Iranian Studies

Context: Various studies in Iran on the role of menopause and age at menarche in breast cancer reported different results. Objectives: The current study aimed to estimate the overall odds ratio and explore the association between early menarche and menopause with breast cancer. Data Sources: Scopus, Web of Science, PubMed, Google Scholar and Iranian databases such as Magiran and SID, breast cancer key journals (Asian pacific journal of cancer prevention, Iranian quarterly journal of breast) and conferences (international breast cancer congresses in Iran, annual breast cancer conferences and seminars in Iran) were searched from 2004 to 2014. Study Selection: The observational studies in Iran that had reported the relationship between menopause and early menarche with breast cancer were searched. The exposure was menopause and early menarche and the outcome was breast cancer with pathological confirmation. Data Extraction: Using strengthening the reporting of observational studies in epidemiology (STROBE) checklist, quality assessment of the articles and data extraction were performed separately by two authors. Results: Of 4396 articles, 12 studies with a sample size of 27734, 11 studies with a sample size of 4039 and 20 studies with a sample size of 53417 were analyzed to estimate the overall odds ratio (OR) for early menarche and the standardized mean difference (SMD) of the average menarche age and overall or of menopause, respectively. A significant relationship was observed between early menarche and breast cancer (OR = 1.57, 95% confidence interval (CI) = 1.05, 2.34). The mean menarche age in patients was also significantly lower than in healthy females (SMD = -0.087, 95%CI = -0.151, -0.02). Postmenopausal female had a higher risk for developing breast cancer; however, this relationship was not statistically significant (OR=1.35, 95%CI=0.98, 1.86). Conclusions: Menopause and early menarche increase the odds of breast cancer. Therefore, breast cancer prevention and screening programs are needed to reduce the burden of this cancer and improve the quality of females‘ lives.