Risk factors for breast cancer in Iranian women aged less than 40 years.

Abstract

This case-control study was carried out in a university-affiliated teaching hospital, Tehran city, Iran. A total of 312 newly diagnosed cases aged less than 40 years old participated and were matched for age and ethnicity with 312 controls. The results showed that in women who never married (OR=2.42 95%CI=1.51-3.88) (P<0.001), had a family history of breast cancer (OR=7.07 95%CI=2.95-16.99) (P<0.001), a low age of menarche (OR=0.1 95% CI=0.04-0.23) (P<0.001)), lower parity (OR=13.3 95% CI=3.89-45.66) (P<0.001) and took oral contraceptive pills (OR= 2.83 95% CI=1.87-4.24) (P<0.000) were at increased risk. A direct association with age at first birth was also evident(P=0.041), with a significantly inverse association between duration of lactation and breast cancer risk (p=0.016). On multivariate logistic regression, parity, family history of breast cancer, use of oral contraceptive pills, and age at first birth remained significant. In women lower than 40 years of age, breast cancer risk was significantly higher in women with parity≥4 compared with nulliparity but no association emerged with history of breast-feeding. Other risk factors were similar to those described in breast cancer epidemiology at any age.