Do reproductive and hormonal risk factors for breast cancer associate with attendance at mammography screening?

To determine whether reproductive and hormonal risk factors for breast cancer associate with mammography attendance. We linked data from the Malmo Diet and Cancer Study to the Malmo mammography register (Sweden, 1992-2009). We analyzed 11,409 women (age 44-72) who were free of breast cancer at study entry and a total of 69,746 screening invitations. Generalized Estimating Equations were used to account for repeated measures within subjects. Models were adjusted for age and other sociodemographic factors. In this study cohort, mammography screening attendance ranged from 87.6 to 94.5 % between calendar years, with an average attendance of 92 %. Higher attendance was found among women who had given birth to fewer than three children (ORs ranging between 1.15 and 1.37) and had used oral contraceptives (OC) within the last decade (OR = 1.22, 95 % CI 1.07-1.38) and for a longer period (OR = 1.13, 95 % CI 1.01-1.27). A lower odds of attendance was found among post-menopausal women (OR = 0.86, 95 % CI 0.77-0.96). Age < 13 at menarche, age a parts per thousand yen30 at first childbirth, age a parts per thousand yen55 at menopause, age < 20 at first OC use, nulliparity, breastfeeding, and hormone replacement therapy were not associated with mammography attendance. Reproductive and hormonal risk factors for breast cancer have little effect on mammography screening attendance. This may indicate a potential for under-screening of some women at higher risk.