“…A positive association between age at menarche and density was reported to be stronger in premenopausal women (El-Bastawissi et al , 2000; Vachon et al , 2000); in some studies (Vachon et al , 2000) these associations were attenuated in multivariate analyses. Hormone replacement therapy (HRT), older age at first child's birth, nulliparity, a family history of breast cancer, and alcohol consumption have been reported to be associated with increased breast density (Gram et al , 1995; El-Bastawissi et al , 2000; Vachon et al , 2000, 2002, 2005; Colacurci et al , 2001; Erel et al , 2001; Rutter et al , 2001; Gapstur et al , 2003; Ziv et al , 2003; Conner et al , 2004; Harvey et al , 2005; Boyd et al , 2006; Maskarinec et al , 2006; Titus-Ernstoff et al , 2006). Inconsistent relations with breast density have been reported for smoking, circulating hormone levels (blood estrogen, estrone levels, total estradiol levels, sex hormone-binding globulin), race/ethnicity, and a few polymorphisms in the estrogen metabolism pathway genes (Boyd et al , 2002; Haiman et al , 2002; Gapstur et al , 2003; Warwick et al , 2003; Conner et al , 2004; Aiello et al , 2005; Noh et al , 2006; Warren et al , 2006; Bremnes et al , 2007; Maskarinec et al , 2007; Tamimi et al , 2007; Verheus et al , 2007).…”