Table 1.

Characteristics of the study population (one random observation per woman, n = 222,019) according to family history. Frequency and column percentage

CharacteristicNo family history n = 144,930 (65%)Second degree only n = 40,253 (18%)First degree only n = 24,028 (11%)First and second degree n = 11,376 (5.1%)Male relativean = 1,432 (0.6%)
Age group, y, n (%)
 35–397,100 (4.9)3,270 (8.1)1,313 (5.5)931 (8.2)79 (5.5)
 40–4422,043 (15)8,118 (20)2,835 (12)1,670 (15)193 (14)
 45–4924,738 (17)7,654 (19)3,536 (15)1,878 (17)265 (19)
 50–5426,259 (18)7,060 (18)3,933 (16)2,006 (18)233 (16)
 55–5922,714 (16)5,478 (14)3,970 (17)1,788 (16)241 (17)
 60–6418,603 (13)4,212 (11)3,572 (15)1,444 (13)173 (12)
 65–6913,022 (9.0)2,769 (6.9)2,645 (11)973 (8.6)147 (10)
 70–7410,451 (7.2)1,692 (4.2)2,224 (9.3)686 (6.0)101 (7.1)
BMI, n (%)
 BMI < 18.52,528 (1.9)559 (1.5)415 (1.8)162 (1.5)24 (1.9)
 18.5 ≤ BMI < 24.954,876 (41)14,968 (39)9,032 (40)4,162 (38)471 (36)
 25.0 ≤ BMI < 29.940,591 (30)11,154 (29)6,813 (30)3,265 (30)404 (31)
 30.0 ≤ BMI < 34.920,240 (15)6,175 (16)3,437 (15)1,740 (16)216 (17)
 BMI ≥ 35.016,591 (12)5,569 (15)2,753 (12)1,586 (15)179 (14)
 [Missing]10,1041,8281,578461138
BI-RADS breast density, n (%)
 Almost entirely fat14,147 (9.8)3,339 (8.3)2,193 (9.1)908 (8.0)149 (10)
 Scattered fibroglandular densities52,532 (36)13,960 (35)8,766 (37)3,987 (35)511 (36)
 Heterogeneously dense60,666 (42)17,724 (44)10,157 (42)5,008 (44)616 (43)
 Extremely dense17,585 (12)5,230 (13)2,912 (12)1,473 (13)156 (11)
Age at first birth, n (%)
 Nulliparous34,640 (25)10,240 (26)5,965 (26)2,848 (26)358 (26)
 Age < 3077,148 (55)20,363 (52)12,772 (55)6,029 (54)762 (55)
 Age ≥ 3029,552 (21)8,702 (22)4,682 (20)2,278 (20)264 (19)
 [Missing]3,59094860922148
Age at menopause, years, n (%)
 Premenopausal44,836 (36)15,616 (44)6,575 (32)3,660 (36)390 (32)
 <4010,407 (8.2)3,328 (9.3)1,831 (8.8)1,158 (12)138 (11)
 40–4930,846 (24)7,376 (21)5,026 (24)2,311 (23)323 (26)
 50–5432,125 (25)7,407 (21)5,775 (28)2,361 (23)305 (25)
 ≥558,257 (6.5)1,950 (5.5)1,598 (7.7)598 (5.9)71 (5.8)
 [Missing]18,4594,5763,2231,288205
Postmenopausal hormones, n (%)
 Yes21,590 (15)6,187 (16)3,304 (14)1,632 (15)168 (12)
 No117,952 (85)32,778 (84)19,789 (86)9,388 (85)1,193 (88)
 [Missing]5,3881,28893535671
Race/ethnicity, n (%)
 White, non-Hispanic94,056 (65)32,844 (82)17,893 (75)9,479 (84)912 (64)
 Black, non-Hispanic6,009 (4.2)1,341 (3.3)990 (4.1)381 (3.4)89 (6.3)
 Asian29,129 (20)2,591 (6.5)3,025 (13)580 (5.1)223 (16)
 American Indian/Alaska Native567 (0.4)153 (0.4)110 (0.5)45 (0.4)8 (0.6)
 Hispanic9,662 (6.7)1,781 (4.4)1,173 (4.9)444 (3.9)135 (9.5)
 Other4,411 (3.1)1,328 (3.3)684 (2.9)398 (3.5)57 (4.0)
 [Missing]1,096215153498
Ovarian cancer in family, n (%)
 Yes6,026 (5.4)2,393 (8.1)1,608 (8.9)999 (12)174 (15)
 No106,024 (95)27,239 (92)16,411 (91)7,696 (89)980 (85)
 [Missing]32,88010,6216,0092,681278
  • NOTE: Proportions may not add to 100% due to rounding.

  • aWomen with a male relative affected by breast cancer were placed in the male relative category regardless of breast cancer among female relatives.