[The risk factors for breast cancer: a case-control study].

In western countries, female breast cancer is a major cause of death. Many risk factors for breast cancer have been identified, but the magnitude of the risks is clearly different between high and low risk areas. In this hospital-based case-control study we evaluated risk factors for female breast cancer in 158 women with breast cancer and 131 controls. Cases presented a later age at first birth and a lower median number of pregnancies. The risk of breast cancer increased with increasing age at first birth, particularly for women with lower parity. After controlling for other variables the risk significantly decreased with abortion history (OR = 0.5, 95% CI: 0.3-0.7) and oral contraception (OR = 0.5, 95% CI: 0.3-0.9). Premenopausal and postmenopausal women presented different risk factors. Among premenopausal cases the risk was lower for parous women (OR = 0.1, 95% CI: 0.0-0.7) and higher for those with a positive family history (OR = 4.5, 95% CI: 1.3-16). Compared to controls, postmenopausal cases only presented a significantly lower rate of abortions (OR = 0.2, 95% CI: 0.1-0.4). The present study shows that these women can be regarded as belonging to an intermediate risk population.