A CASE-CONTROL STUDY OF RISK-FACTORS FOR BREAST-CANCER IN BRAZIL, 1978-1987

Background. There are still controversies regarding the role of many r isk factors assessed for breast cancer worldwide. In Brazil, it repres ents a major cause of death among women but yet few analytical studies have been published to date. Methods. The association of selected fac tors with breast cancer was assessed in a case-control study of 300 wo men, aged 25-75 years, treated at the Federal University Hospital, Bel o Horizonte, Brazil, from 1978 to 1987. In all, 300 cases with diagnos ed breast carcinoma were compared with 600 controls matched an age and date of diagnosis. Socioeconomic, demographic and reproductive factor s were analysed. Results. Multiple logistic regression analysis showed the following factors to be independently associated with increased r isk 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 degre e female relatives (OR = 9.35, 95% CI : 3.22-27.14); and e) oral contr aceptive use (OR = 1.81, 95% CI : 1.15-2.85). Irregular menstrual cycl e (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/p rotective factors previously demonstrated elsewhere in the world and p rovides clear documentation of breast cancer epidemiology in Brazil.