Table 2.
Relation of participant characteristics with mammographic percent density (MPD) in quartiles among controls (n = 165).
| Quartile 1: <7.8% | Quartile 2: 7.8% to <16.9% | Quartile 3: 16.9% to <30.8% | Quartile 4: ≥30.8% | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Participant Characteristics | N | % | N | % | N | % | N | % | p-Value * |
| Age: Median (range) | 53.3 | (32.7, 68.5) | 53.6 | (35.4, 69.1) | 50.4 | (30.2,70.8) | 48.5 | (30.5, 64.8) | 0.018 ** |
| Race | |||||||||
| White | 11 | 26.8 | 11 | 26.2 | 14 | 35.0 | 15 | 35.7 | 0.93 † |
| Black | 28 | 68.3 | 30 | 71.4 | 25 | 62.5 | 26 | 61.9 | |
| Other | 2 | 4.9 | 1 | 2.4 | 1 | 2.5 | 1 | 2.4 | |
| BMI, kg/m2 | |||||||||
| <25 | 2 | 5.0 | 4 | 9.5 | 10 | 25.0 | 20 | 47.6 | <0.0001 |
| 25–30 | 9 | 22.5 | 11 | 26.2 | 15 | 37.5 | 11 | 26.2 | |
| 30+ | 29 | 72.5 | 27 | 64.3 | 15 | 37.5 | 11 | 26.2 | |
| Education | |||||||||
| At most, high school/GED | 12 | 29.3 | 15 | 35.7 | 10 | 25.0 | 9 | 21.4 | 0.86 |
| Some college/postsecondary courses | 15 | 36.6 | 13 | 31.0 | 14 | 35.0 | 17 | 40.5 | |
| College/graduate school | 14 | 34.2 | 14 | 33.3 | 16 | 40.0 | 16 | 38.1 | |
| Age at menarche | |||||||||
| ≤12 | 30 | 75.0 | 21 | 50.0 | 21 | 52.5 | 22 | 52.4 | 0.14 |
| 13 | 6 | 15.0 | 14 | 33.3 | 9 | 22.5 | 9 | 21.4 | |
| 14+ | 4 | 10.0 | 7 | 16.7 | 10 | 25.0 | 11 | 26.2 | |
| Age at first birth | |||||||||
| Nulliparous/≥30 | 14 | 34.2 | 15 | 35.7 | 11 | 27.5 | 14 | 33.3 | 0.87 |
| <30 | 27 | 65.9 | 27 | 64.3 | 29 | 72.5 | 28 | 66.7 | |
| Menopausal status | |||||||||
| Premenopausal | 17 | 41.5 | 21 | 50.0 | 26 | 65.0 | 29 | 69.1 | 0.039 |
| Postmenopausal | 24 | 58.5 | 21 | 50.0 | 14 | 35.0 | 13 | 31.0 | |
| Any first degree relative with breast cancer | |||||||||
| No | 32 | 78.1 | 35 | 83.3 | 35 | 87.5 | 31 | 73.8 | 0.42 |
| Yes | 9 | 22.0 | 7 | 16.7 | 5 | 12.5 | 11 | 26.2 | |
| BI-RADS breast density | |||||||||
| a (entirely fat) | 26 | 63.4 | 11 | 26.2 | 3 | 7.5 | 1 | 2.4 | <0.0001 |
| b (scattered densities) | 15 | 36.6 | 28 | 66.7 | 21 | 52.5 | 15 | 35.7 | |
| c (heterogeneously dense) | 0 | 0.0 | 2 | 4.8 | 15 | 37.5 | 20 | 47.6 | |
| d (extremely dense) | 0 | 0.0 | 1 | 2.4 | 1 | 2.5 | 6 | 14.3 | |
| Quartiles of baseline sound speed (m/s) | |||||||||
| <1440.63 | 17 | 41.5 | 16 | 38.1 | 7 | 17.5 | 0 | 0.0 | <0.0001 |
| 1440.63 to <1445.65 | 18 | 43.9 | 12 | 28.6 | 8 | 20.0 | 5 | 11.9 | |
| 1445.65 to <1452.81 | 6 | 14.6 | 13 | 30.9 | 15 | 37.5 | 7 | 16.7 | |
| ≥1452.81 | 0 | 0.0 | 1 | 2.4 | 10 | 25.0 | 30 | 71.4 | |
Quartiles based upon distribution among controls; * p-values from Chi-square test except where noted; ** Kruskal–Wallis test; † Fisher’s exact test.