Table 1.
Baseline characteristics of study population by menopausal status and current postmenopausal hormone use
| Premenopausal
|
Postmenopausal, estrogen only
|
Postmenopausal, estrogen+progesterone
|
Postmenopausal, no hormone use
|
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cases (n = 948) | Controls (n = 1488) | p valuea | Cases (n = 281) | Controls (n = 438) | p valuea | Cases (n = 463) | Controls (n = 542) | p valuea | Cases (n = 904) | Controls (n = 1591) | p valuea | |
| Mean (SD) | ||||||||||||
| Percent breast density | 42.6 (19.7) | 36.6 (20.3) | <0.001 | 33.6 (18.4) | 26.5 (18.3) | <0.001 | 35.8 (19.0) | 29.7 (19.3) | <0.001 | 24.8 (17.5) | 21.1 (16.9) | <0.001 |
| Dense area, cm2 | 63.0 (40.6) | 53.6 (37.4) | <0.001 | 59.0 (42.7) | 47.4 (44.1) | <0.001 | 60.3 (42.0) | 46.9 (34.5) | <0.001 | 46.8 (38.9) | 36.5 (31.4) | <0.001 |
| Non-dense area, cm2 | 105.6 (81.9) | 119.4 (94.1) | <0.001 | 132.5 (95.6) | 148.7 (98.8) | 0.008 | 123.2 (85.1) | 136.5 (95.8) | 0.04 | 165.6 (112.9) | 166.5 (115.2) | 0.70 |
| Age at mammogram, years | 45.1 (4.5) | 45.2 (4.4) | 0.94 | 60.1 (8.0) | 59.2 (8.5) | 0.12 | 58.7 (7.1) | 58.6 (7.8) | 0.68 | 62.8 (8.6) | 62.4 (8.5) | 0.30 |
| Age at diagnosis, years | 49.6 (5.3) | NA | 64.9 (8.4) | NA | 62.8 (7.5) | NA | 67.4 (8.6) | NA | ||||
| Body mass index, kg/m2 | 24.9 (5.0) | 25.0 (5.3) | 0.55 | 26.1 (5.0) | 25.9 (5.2) | 0.63 | 24.9 (4.4) | 24.6 (4.7) | 0.09 | 27.3 (6.0) | 26.1 (5.6) | <0.001 |
| Frequency (%) | ||||||||||||
| Body mass index, kg/m2 | 0.32 | 0.47 | 0.44 | <0.001 | ||||||||
| <25 | 562 (59.3%) | 927 (62.3%) | 131 (46.6%) | 225 (51.4%) | 273 (59.0%) | 341 (62.9%) | 354 (39.2%) | 794 (49.9%) | ||||
| 25–29 | 233 (24.6%) | 339 (22.8%) | 90 (32.0%) | 134 (30.6%) | 119 (25.7%) | 137 (25.3%) | 290 (32.1%) | 499 (31.4%) | ||||
| 30–34 | 87 (9.2%) | 116 (7.8%) | 36 (12.8%) | 51 (11.6%) | 41 (8.9%) | 42 (7.7%) | 133 (14.7%) | 180 (11.3%) | ||||
| 35+ | 44 (4.6%) | 88 (5.9%) | 17 (6.0%) | 28 (6.4%) | 15 (3.2%) | 21 (3.9%) | 89 (9.8%) | 116 (7.3%) | ||||
| Unknown | 22 (2.3%) | 18 (1.2%) | 7 (2.5%) | 0 | 15 (3.2%) | 1 (0.2%) | 38 (4.2%) | 2 (0.1%) | ||||
| Parity | 0.60 | 0.84 | 0.56 | 0.11 | ||||||||
| Nulliparous | 254 (26.8%) | 381 (25.6%) | 46 (16.4%) | 74 (16.9%) | 132 (28.5%) | 150 (27.7%) | 190 (21.0%) | 288 (18.1%) | ||||
| Parous | 678 (71.5%) | 1072 (72.0%) | 230 (81.9%) | 355 (81.1%) | 307 (66.3%) | 376 (69.4%) | 690 (76.3%) | 1242 (78.1%) | ||||
| Unknown | 16 (1.7%) | 35 (2.4%) | 5 (1.8%) | 9 (2.1%) | 24 (5.2%) | 16 (3%) | 24 (2.7%) | 61 (3.8%) | ||||
| Family history of breast cancer | <0.001 | 0.45 | 0.10 | <0.001 | ||||||||
| No | 770 (81.2%) | 1314 (88.3%) | 230 (81.9%) | 372 (84.9%) | 379 (81.9%) | 472 (87.1%) | 671 (74.2%) | 1334 (83.8%) | ||||
| Yes | 164 (17.3%) | 172 (11.6%) | 49 (17.4%) | 66 (15.1%) | 74 (16.0%) | 69 (12.7%) | 226 (25.0%) | 257 (16.2%) | ||||
| Unknown | 14 (1.5%) | 2 (0.1%) | 2 (0.7%) | 0 | 10 (2.2%) | 1 (0.2%) | 7 (0.8%) | 0 | ||||
NA not applicable
a
p values are Kruskal-Wallis test for continuous, Wilcoxon test for BMI categories, and Chi-square test for discrete. Missing values not included in the tests