Abstract
The association between breastfeeding and the risk of breast cancer was studied as part of a Dutch population-based epidemiological study of the aetiology of female breast cancer. A total of 484 breast cancer patients and 484 controls (matched for age; age range: 20-54 years) were compared with regard to their breastfeeding habits. There was no clear association between breastfeeding and breast cancer risk. After adjustment for confounders women who had ever breastfed had no lower risk of breast cancer than women who never had given breastfeeding. Women who had breastfed for prolonged periods (total lifetime nursing of 44 weeks or more) had, after adjustment for confounders, a 29% lower risk of breast cancer compared to women who had never breastfed, but this risk reduction was not statistically significant. These results do not support the hypothesis that (short) periods of breastfeeding reduce the risk of breast cancer in young women. A possible protective effect of longer periods of breastfeeding, which is suggested more strongly in the literature, could not be investigated in this study because the women breastfed their children for relatively short periods.