Risk factors for benign breast disease: a case-control study of discordant twins.

ABSTRACT

PIP: The influences of potential risk factors for benign breast disease (BBD) were assessed using women twins in a matched pair design. 2 groups of cases from the Kaiser Permanente Twin Registry were considered: 90 pairs of female twins in which 1 twin reported a history of BBD confirmed by biopsy and her twin reported no such history, and 48 pairs of female twins in which the case had clinically diagnosed fibrocystic BBD and the twin was free of disease at examination and reported no history of the disease. Results were similar in those 2 samples. A significantly positive association was found between BBD and coffee consumption. Oral contraceptive use and greater body mass were inversely associated with BBD after controlling for possible confounding variables by matched pairs multiple logistic analysis. All associations were stronger for monozygotic than dizygotic pairs. Twin pairs discordant for disease provide an excellent sample in which to assess the importance for potential risk factors while controlling for early environmental and genetic backgrounds.