Table 1.
Characteristics of 964 women recruited during annual screening mammography at the Joanne Knight Breast Health Center, Washington University School of Medicine, St. Louis, MO.*
| Total (N=964) | Nulliparous (N=228) | Parous never breastfed (N=289) | 0–6 months (N=115) | 7–12 months (N=91) | >12 months (N=241) | p | |
|---|---|---|---|---|---|---|---|
| N (%) or mean (SD) | N (%) or mean (SD) | N (%) or mean (SD) | N (%) or mean (SD) | N (%) or mean (SD) | N (%) or mean (SD) | ||
|
| |||||||
| Age, year | 50.7 (7.1) | 48.8 (7.1) | 52.2 (6.7) | 52.1 (7.0) | 53.3 (6.9) | 49.2 (6.8) | <0.0001 |
| Age at menarche, year | 12.7 (1.6) | 12.6 (1.5) | 12.7 (1.7) | 12.8 (1.6) | 12.6 (1.6) | 12.9 (1.6) | 0.31 |
| Age at first birth, year a | 25.6 (6.2) | - | 23.3 (6.1) | 27.3 (6.4) | 26.0 (5.8) | 27.3 (5.4) | <0.0001 |
| Body Mass Index, kg/m2 | 30.6 (7.8) | 31.2 (8.8) | 32.4 (7.9) | 30.0 (6.1) | 29.6 (7.1) | 28.5 (7.2) | <0.0001 |
| Race | |||||||
| Non-Hispanic white | 645 (66.9) | 176 (77.2) | 140 (48.4) | 73 (63.5) | 66 (72.5) | 190 (78.8) | |
| Non-Hispanic black | 279 (28.9) | 43 (18.9) | 144 (49.8) | 38 (33.0) | 20 (22.0) | 34 (14.1) | <0.0001 |
| Other Race | 40 (4.2) | 9 (4.0) | 5 (1.7) | 4 (3.5) | 5 (5.5) | 17 (7.1) | |
| Menopause status | |||||||
| Premenopausal | 613 (63.6) | 167 (73.3) | 157 (54.3) | 63 (54.8) | 46 (50.6) | 180 (74.7) | <0.0001 |
| Postmenopausal | 351 (36.4) | 61 (26.8) | 132 (45.7) | 52 (45.2) | 45 (49.5) | 61 (25.3) | |
| Family history of breast cancer | |||||||
| Yes | 228 (23.7) | 65 (28.5) | 52 (18.0) | 27 (23.5) | 30 (33.0) | 54 (22.4) | 0.01 |
| No | 736 (76.4) | 163 (71.5) | 237 (82.0) | 88 (76.5) | 61 (67.0) | 187 (77.6) | |
| Parity number | |||||||
| Nulliparous | 228 (23.7) | 228 (100) | - | - | - | - | |
| 1–2 children | 480 (49.8) | - | 210 (72.7) | 90 (78.3) | 63 (69.2) | 117 (48.6) | <0.0001b |
| ≥3 children | 256 (26.6) | - | 79 (27.3) | 25 (21.7) | 28 (30.8) | 124 (51.5) | |
| Current alcohol use c | |||||||
| Yes | 627 (65.2) | 152 (66.7) | 155 (53.8) | 79 (69.3) | 64 (70.3) | 177 (73.4) | <0.0001 |
| No | 335 (34.8) | 76 (33.3) | 133 (46.2) | 35 (30.7) | 27 (29.7) | 64 (26.6) | |
| Mammographic density d | |||||||
| Volumetric Percent density, % | 8.5 (6.4) | 9.4 (7.3) | 6.8 (4.9) | 7.6 (4.9) | 9.0 (6.5) | 9.9 (7.3) | <0.0001 |
| Dense volume, cm3 | 96.1 (83.9) | 104.2 (92.3) | 103.6 (95.0) | 87.4 (56.0) | 104.1 (111.0) | 80.5 (53.2) | 0.02 |
| Non-dense volume, cm3 | 1450.4 (1423.7) | 1442.5 (1502.8) | 1777.6 (1666.7) | 1416.5 (1319.7) | 1318.7(1105.0) | 1131.5 (1067.8) | <0.0001 |
| Log10-Mammographic density | |||||||
| Volumetric Percent density, % | 0.8 (0.3) | 0.9 (0.3) | 0.8 (0.2) | 0.8 (0.2) | 0.9 (0.3) | 0.9 (0.3) | <0.0001 |
| Dense volume, cm3 | 1.9 (0.3) | 1.9 (0.3) | 1.9 (0.3) | 1.9 (0.2) | 1.9 (0.3) | 1.8 (0.2) | 0.02 |
| Non-dense volume, cm3 | 3.0 (0.4) | 3.0 (0.4) | 3.1 (0.4) | 3.0 (0.3) | 3.0 (0.3) | 2.9 (0.4) | <0.0001 |
*
Presented as N. (%) for categorical variables or mean (SD) for continuous variables. N = Number, % = column percentage, SD = standard deviation
a.
4 parous women were missing age at first birth
b.
Chi-square test across parous never breastfed, 0–6 months, 7–12 months, and >12 months groups.
c.
2 participants are missing alcohol use information
d.
Mammographic density indicators are not normally distributed. Kruskal-Wallis tests were conducted instead of ANOVA. These indicators were log10 transformed to follow approximately normal distributions.