Reproductive factors affect breast cancer risk, but less is known of
their associations with mammographic density and whether these differ by
menopausal status. We report on a cross-sectional study of 1946 pre- and
3047 post-menopausal women who joined a breast screening programme in
Northern Greece during 1993-1997. The odds of having a high-density
Wolfe pattern (P2/DY) was inversely associated with age (P for linear
trend < 0.001) in both pre- and post-menopausal women and, for
post-menopausal women, with years since menopause (P < 0.001). The odds
of a P2/DY pattern declined with higher parity (P < 0.001) and younger
age at first pregnancy (P = 0.05) in both pre- and post-menopausal
women. They also decreased with the duration of breast-feeding in
pre-menopausal women (P = 0.03 in pre- and P = 0.69 in post-menopausal
women; test for interaction with menopausal status: P = 0.07). Age at
menarche, age at menopause and the number of miscarriages/abortions were
not associated with mammographic density. Age at first pregnancy and
parity were strong correlates of mammographic density in pre- and
post-menopausal women while duration of breast-feeding appeared to be
particularly important in pre-menopausal women. (c) 2005 Elsevier Ltd.
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