Physiological, Reproductive Factors and Breast Cancer Risk in Jiangsu Province of China

To evaluate the relationship between physiological, reproductive factors and risk of breast cancer, we conducted a case-control study with 669 cases and 682 population-based controls in Jiangsu Province of China. A structured questionnaire was used to elicit detailed information. All subjects completed an in-person interview. Unconditional logistic regression analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs) as measures of risk for breast cancer. The results have revealed that there was an increasing risk of breast cancer, include early age at menarche(<= 13 year), late age at menopause(>50 year) and older age at first pregnancy (>= 30 year). Breastfeeding was associated significantly with a reduced risk of breast cancer. Women who had history of breastfeeding were at significantly decreased OR (0.44, 95%CI: 0.27-0.73). The protective effects of breastfeeding for breast cancer seemed greater for women who had extended duration of breastfeeding during their lifetime (p for linear trend: 0.0095). These results suggested that physiological and reproductive factors may play important roles in the development of breast cancer among Jiangsu' women of China.