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, weconducted 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% confidenceintervals (CIs) as measures of risk for breast cancer. The results have revealed that there was an increasing riskof breast cancer, include early age at menarche(≤13 year), late age at menopause(>50 year) and older age at firstpregnancy (≥30 year). Breastfeeding was associated significantly with a reduced risk of breast cancer. Womenwho had history of breastfeeding were at significantly decreased OR (0.44, 95%CI: 0.27-0.73). The protectiveeffects of breastfeeding for breast cancer seemed greater for women who had extended duration of breastfeedingduring their lifetime (p for linear trend: 0.0095). These results suggested that physiological and reproductivefactors may play important roles in the development of breast cancer among Jiangsu’ women of China.