Risk factors for breast cancer among pre- or post-menopausal women in Belo Horizonte, Brazil.

BACKGROUND: Much controversy has been generated about pre- and post-menopausal breast cancer patients and investigators have sought to identify whether risk factors differ between these two groups. In Brazil, breast cancer is an important cause of death among women and there are few analytical studies concerning pre- or post-menopausal comparisons. METHODS: A case-control study was carried out at the Federal University Hospital, Belo Horizonte, Brazil, to determine if selected socio-economic and reproductive risk factors for breast cancer differed between pre-menopausal and post-menopausal women. Cases were 300 women with breast carcinoma and controls were 600 women with other benign diseases matched for age and date of diagnosis, admitted to the same hospital during the same period (1978-1987). Univariate and multivariate conditional logistic regression analyses were performed. RESULTS: Multivariate analysis showed no differences in breast cancer risk in pre- and post-menopausal women (risk factors were similar in direction and magnitude). Occupation, irregular menstrual cycles, parity, history of breast cancer in at least one first-degree female relative, and oral contraceptive use had similar associations in both groups. CONCLUSIONS: The present study indicates that breast cancer diagnosed before and after menopause has a similar risk profile.

A case-control study of risk factors for breast cancer in Brazil, 1978-1987.

BACKGROUND: There are still controversies regarding the role of many risk factors assessed for breast cancer worldwide. In Brazil, it represents a major cause of death among women but yet few analytical studies have been published to date. METHODS: The association of selected factors with breast cancer was assessed in a case-control study of 300 women, aged 25-75 years, treated at the Federal University Hospital, Belo Horizonte, Brazil, from 1978 to 1987. In all, 300 cases with diagnosed breast carcinoma were compared with 600 controls matched on age and date of diagnosis. Socio-economic, demographic and reproductive factors were analysed. RESULTS: Multiple logistic regression analysis showed the following factors to be independently associated with increased risk of breast cancer: a) monthly family income (odds ratio [OR] = 1.69, 95% confidence interval [CI]: 1.18-2.42); b) being a housewife (OR = 2.86, 95% CI: 1.83-4.47; c) parity of less than six deliveries and nulliparous women (OR = 5.06, 95% CI: 3.01-8.52 and OR = 2.42, CI: 1.64-3.59, respectively); d) history of breast cancer among first degree female relatives (OR = 9.35, 95% CI: 3.22-27.14); and e) oral contraceptive use (OR = 1.81, 95% CI: 1.15-2.85). Irregular menstrual cycle (OR = 0.44, 95% CI: 0.25-0.75) was associated with breast cancer as a protective effect. CONCLUSIONS: The study has confirmed most risk/protective factors previously demonstrated elsewhere in the world and provides clear documentation of breast cancer epidemiology in Brazil.