Protective effect of longstanding lactation and reproductive factors: a case–control study in North Tanzania

Reproductive risk factors and associated risk for breast cancer have been and remain the subject of intense investigation. Particular attention is given to examining increased breast cancer risk in pre- and post-menopausal women who, because of their particular ovarian function, may experience a prolonged exposure to higher concentrations of endogenous estrogen during the reproductive cycles of menarche, pregnancy, and menopause. Specifically, associations exist between the risk factors of nulliparity, early age at menarche, late age at menopause, and late age at first full-term pregnancy and increased risk for breast cancer [1]. There is also mounting evidence that multi-parity and breastfeeding may affect breast cancer risk independently, although findings are inconsistent at times. Most of what the authors currently know concerning the associations of these risk factors and increased risk for breast cancer are the results of studies performed in highincome countries, with little investigation done and therefore, little known, in less developed countries, especially Africa. Work reported in this journal by Jordan and coworkers from a case–control study on breast cancer risk factors in Tanzania, East Africa , found that both age at menarche and lifelong lactation have inverse associations with breast cancer in pre-menopausal women, and that late age at first full-term pregnancy is associated with elevated breast cancer risk in post-menopausal women. Although these findings agree with the literature, the study suffers from limited statistical power (115 cases and 230 controls), especially after stratification by menopausal status. Nonetheless, the study underscores the need for well-designed studies to examine reproductive factors and breast cancer risk in larger cohorts of African women.