Risk of breast cancer, diet and internal migrations in northern Italy

The protective effect of birth in southern Italy as opposed to other regions was evaluated in a population-based case-control study of diet and breast cancer among residents in the province of Vercelli. Cases were 250 women with breast cancer diagnosed during 1983-1984 and controls 499 women randomly selected from the general population. The crude relative risk of breast cancer for women born in the south was 0.76 (95% confidence interval, 0.43-1.3). After adjustment for dietary and other potential confounders in multivariate analyses, the protective effect of place of birth disappeared (RR 1.0; 95% CI, 0.57-1.9). The study indicates that north-south differences in the incidence of breast cancer in Italy may in large part be attributed to different dietary habits.