Table 2.

Characteristics of mammograms for 1,274 study subjects

Case
Control
All
n (%)n (%)n (%)
No. mammograms1,956 (54.7)1,619 (45.3)3,575 (100.0)
Age at mammogram
    <40 y7 (0.4)14 (0.9)21 (0.6)
    40-44 y73 (3.7)62 (3.8)135 (3.8)
    45-49 y227 (11.6)196 (12.1)423 (11.8)
    50-54 y352 (18.0)357 (22.1)709 (19.8)
    55-59 y378 (19.3)251 (15.5)629 (17.6)
    60-64 y377 (19.3)247 (15.3)624 (17.5)
    65-69 y311 (15.9)259 (16.0)570 (15.9)
    70-74 y182 (9.3)154 (9.5)336 (9.4)
    75+ y49 (2.5)79 (4.9)128 (3.5)
Menopausal status
    Premenopausal246 (12.6)390 (24.1)636 (17.8)
    Perimenopausal163 (8.3)76 (4.7)239 (6.7)
    Postmenopausal1,547 (79.1)1,153 (71.2)2,700 (75.5)
HRT use
    None867 (44.3)754 (46.6)1,621 (45.3)
    Estrogen only497 (25.4)525 (32.4)1,022 (28.6)
    Estrogen plus progesterone592 (30.3)340 (21.0)932 (26.1)

Mean (SD)
Mean (SD)
Mean (SD)
Percent density
    All mammograms37.0 (22.2)29.4 (21.7)33.0 (22.2)
    <40 y59.1 (26.1)45.1 (26.5)50.0 (26.6)
    40-44 y59.5 (19.1)42.6 (24.7)51.8 (23.3)
    45-49 y49.1 (22.9)39.3 (24.4)44.6 (24.1)
    50-54 y41.9 (23.3)33.4 (22.5)37.7 (23.3)
    55-59 y36.7 (21.1)29.1 (20.1)33.6 (21.0)
    60-64 y32.8 (19.7)26.4 (21.8)30.3 (20.8)
    65-69 y31.8 (21.6)24.7 (21.7)28.6 (21.9)
    70-74 y31.0 (21.6)21.9 (17.7)26.8 (20.4)
    75+ y36.1 (26.3)24.2 (18.0)28.9 (22.4)
    Premenopausal50.6 (23.2)38.7 (25.0)43.3 (25.0)
    Perimenopausal46.0 (21.7)36.8 (19.4)43.1 (21.4)
    Postmenopausal35.1 (22.0)26.6 (20.8)31.5 (21.9)