Background
Methods
Study population
Mammographic density
Selected breast cancer risk factors
Statistical analysis
Results
Premenopausal | Postmenopausal | |||
---|---|---|---|---|
Cases
N = 559 | Controls
N = 1727 | Cases
N = 731 | Controls
N = 1695 | |
Mean (SD) | ||||
Agea
| 46.2 (4.6) | 46.1 (4.3) | 60.1 (7.0) | 59.6 (7.4) |
Current BMI (kg/m2) | 25.2 (4.8) | 25.4 (5.1) | 25.9 (4.6) | 26.1 (5.0) |
Childhood somatotype | 2.5 (1.2) | 2.6 (1.2) | 2.2 (1.2) | 2.4 (1.3) |
Adolescent somatotype | 2.8 (1.0) | 2.9 (1.1) | 2.5 (1.1) | 2.7 (1.2) |
BMI at age 18 (kg/m2) | 20.8 (2.5) | 21.1 (2.7) | 20.9 (2.4) | 21.1 (2.7) |
Weight change since 18 (lbs) | 26.7 (25.8) | 26.3 (25.7) | 29.7 (25.4) | 29.7 (26.8) |
Age at menarche | 12.3 (1.4) | 12.4 (1.4) | 12.5 (1.4) | 12.6 (1.4) |
Parity (among parous) | 2.4 (1.0) | 2.5 (1.0) | 3.2 (1.5) | 3.2 (1.5) |
Age at first birth (among parous) | 26.3 (4.4) | 25.9 (4.1) | 25.6 (3.7) | 25.2 (3.5) |
Breastfeeding (months) (among parous women who ever breastfed) | 16.3 (10.6) | 17.1 (11.1) | 12.6 (10.8) | 11.4 (9.5) |
Birth index | 46.0 (26.4) | 46.7 (25.9) | 56.4 (37.4) | 55.8 (37.7) |
Height (inches) | 65.1 (2.6) | 64.9 (2.5) | 64.5 (2.3) | 64.6 (2.4) |
Alcohol use (g/day) | 4.2 (6.9) | 4.2 (6.3) | 5.0 (7.5) | 4.8 (7.8) |
Age at menopause (y) | 47.8 (5.8) | 46.7 (6.5) | ||
Percent density | 46.1 (18.7) | 39.7 (19.0) | 29.2 (17.6) | 24.8 (17.2) |
Dense area (cm2) | 96.8 (57.5) | 81.3 (50.8) | 50.7 (38.4) | 47.1 (38.9) |
Non-dense area (cm2) | 121.4 (77.0) | 134.4 (80.4) | 141.3 (90.3) | 157.5 (91.1) |
N (percent) | ||||
Nulliparous | 81 (14.5) | 228 (13.2) | 65 (8.9) | 139 (8.2) |
Ever breastfed (among parous) | 361 (76.5) | 1136 (76.9) | 389 (53.6) | 940 (55.8) |
Personal history of BBD | ||||
Confirmed by biopsy | 154 (27.5) | 287 (16.6) | 193 (26.4) | 382 (22.5) |
Unconfirmed/unknown | 170 (30.4) | 566 (32.8) | 190 (26.0) | 423 (25.0) |
Family history of breast cancer | 67 (12.0) | 146 (8.5) | 132 (18.1) | 225 (13.3) |
Hormone therapy usea
| ||||
Never | 191 (26.1) | 547 (32.3) | ||
Current | 401 (54.9) | 789 (46.5) | ||
Past | 139 (19.0) | 359 (21.2) |
Selected risk factor | OR (95 % CI)
not adjusted for MD | OR (95 % CI) adjusted for MD | Percent mediated by MD (p value) |
---|---|---|---|
Childhood somatotypea
Per 1-unit increase | |||
Percent MDc
| 0.93 (0.86,1.01) | 0.98 (0.90,1.07) | 71 % (p = 0.12) |
Dense areac
| 0.93 (0.86,1.01) | 0.95 (0.88,1.04) | 30 % (p = 0.14) |
Non-dense areac
| 0.93 (0.86,1.01) | 0.96 (0.88,1.04) | 35 % (p = 0.16) |
Adolescent somatotypea
Per 1-unit increase | |||
Percent MDc
| 0.90 (0.82,0.99) | 0.97 (0.88,1.07) | 73 % (p = 0.05) |
Dense areac
| 0.90 (0.82,0.99) | 0.92 (0.84,1.01) | 22 % (p = 0.09) |
Non-dense areac
| 0.90 (0.82,0.99) | 0.94 (0.85,1.03) | 35 % (p = 0.11) |
BMI at age 18 (kg/m2)a
Per 5-unit increase | |||
Percent MDc
| 0.80 (0.65,0.97) | 0.96 (0.78,1.19) | 82 % (p = 0.04) |
Dense areac
| 0.80 (0.65,0.97) | 0.83 (0.68,1.02) | 18 % (p = 0.10) |
Non-dense areac
| 0.80 (0.65,0.97) | 0.87 (0.70,1.08) | 40 % (p = 0.11) |
Weight change since 18b
Per 20-lb increase | |||
Percent MDc
| 1.03 (0.96,1.12) | 1.16 (1.06,1.26) | Not mediatedd
|
Dense areac
| 1.03 (0.96,1.12) | 1.05 (0.97,1.13) | Not mediatedd
|
Non-dense areac
| 1.03 (0.96,1.12) | 1.12 (1.02,1.23) | Not mediatedd
|
BMI (kg/m2) Per 5-unit increase | |||
Percent MDc
| 1.03 (0.92,1.16) | 1.22 (1.07,1.39) | Not mediatedd
|
Dense areac
| 1.03 (0.92,1.16) | 1.05 (0.93,1.19) | Not mediatedd
|
Non-dense areac
| 1.03 (0.92,1.16) | 1.16 (1.01,1.33) | Not mediatedd
|
Height Per 3-inch increase | |||
Percent MDc
| 1.14 (1.01,1.28) | 1.14 (1.01,1.29) | Not mediatedd
|
Dense areac
| 1.14 (1.01,1.28) | 1.13 (1.00,1.27) | 6 % (p = 0.43) |
Non-dense areac
| 1.14 (1.01,1.28) | 1.15 (1.02,1.30) | Not mediatedd
|
Age at menarche Per 2-year increase | |||
Percent MDc
| 0.85 (0.74,0.98) | 0.83 (0.72,0.96) | Not mediatedd
|
Dense areac
| 0.85 (0.74,0.98) | 0.83 (0.72,0.96) | Not mediatedd
|
Non-dense areac
| 0.85 (0.74,0.98) | 0.84 (0.73,0.97) | Not mediatedd
|
Nulliparous Nulliparous vs parous | |||
Percent MDc
| 1.15 (0.86,1.52) | 1.07 (0.80,1.42) | 52 % (p = 0.35) |
Dense areac
| 1.15 (0.86,1.52) | 1.11 (0.84,1.48) | 23 % (p = 0.43) |
Non-dense areac
| 1.15 (0.86,1.52) | 1.11 (0.84,1.48) | 22 % (p = 0.37) |
Birth index Per 102-unit increase | |||
Percent MDc
| 0.66 (0.43,1.01) | 0.77 (0.50,1.19) | 38 % (p = 0.08) |
Dense areac
| 0.66 (0.43,1.01) | 0.69 (0.45,1.07) | 13 % (p = 0.21) |
Non-dense areac
| 0.66 (0.43,1.01) | 0.71 (0.46,1.09) | 18 % (p = 0.11) |
Parity (among parous) Per one-child increase | |||
Percent MDc
| 1.00 (0.90,1.12) | 1.03 (0.92,1.16) | Not mediatedd
|
Dense areac
| 1.00 (0.90,1.12) | 1.02 (0.91,1.14) | Not mediatedd
|
Non-dense areac
| 1.00 (0.90,1.12) | 1.01 (0.90,1.13) | Not mediatedd
|
Age at first birth (among parous) Per 5-year increase | |||
Percent MDc
| 1.18 (1.03,1.36) | 1.18 (1.02,1.36) | 3 % (p = 0.58) |
Dense areac
| 1.18 (1.03,1.36) | 1.19 (1.03,1.38) | Not mediatedd
|
Non-dense areac
| 1.18 (1.03,1.36) | 1.18 (1.02,1.36) | 3 % (p = 0.28) |
Breastfeeding (among parous) Ever vs never | |||
Percent MDc
| 0.99 (0.76,1.28) | 1.00 (0.77,1.30) | 89 % (p = 0.92) |
Dense areac
| 0.99 (0.76,1.28) | 0.98 (0.75,1.28) | Not mediatedd
|
Non-dense areac
| 0.99 (0.76,1.28) | 1.00 (0.77,1.30) | 75 % (p = 0.92) |
Breastfeeding (among parous who ever breastfed) Per 12-month increase | |||
Percent MDc
| 0.95 (0.81,1.11) | 0.93 (0.80,1.08) | Not mediatedd
|
Dense areac
| 0.95 (0.81,1.11) | 0.93 (0.79,1.08) | Not mediatedd
|
Non-dense areac
| 0.95 (0.82,1.11) | 0.95 (0.82,1.11) | 1 % (p = 0.92) |
Alcohol use Per 10 g/day increase | |||
Percent MDc
| 0.98 (0.84,1.15) | 0.98 (0.84,1.14) | Not mediatedd
|
Dense areac
| 0.98 (0.84,1.15) | 0.97 (0.83,1.14) | Not mediatedd
|
Non-dense areac
| 0.98 (0.84,1.15) | 0.98 (0.84,1.15) | Not mediatedd
|
Family history of breast cancer Yes vs no | |||
Percent MDc
| 1.47 (1.07,2.01) | 1.46 (1.06,2.00) | 2 % (p = 0.76) |
Dense areac
| 1.47 (1.07,2.01) | 1.39 (1.01,1.92) | 14 % (p = 0.12) |
Non-dense areac
| 1.47 (1.07,2.01) | 1.51 (1.10,2.07) | Not mediatedd
|
History of biopsy-confirmed BBD Yes vs no | |||
Percent MDc
| 2.04 (1.59,2.62) | 1.81 (1.40,2.32) | 17 % (p < 0.01) |
Dense areac
| 2.04 (1.59,2.62) | 1.80 (1.40,2.32) | 18 % (p < 0.01) |
Non-dense areac
| 2.04 (1.59,2.62) | 2.00 (1.56,2.57) | 3 % (p = 0.07) |
History of unconfirmed BBD Yes vs no | |||
Percent MDc
| 1.12 (0.89,1.41) | 1.03 (0.82,1.30) | 73 % (p = 0.34) |
Dense areac
| 1.12 (0.89,1.41) | 1.01 (0.81,1.28) | 87 % (p = 0.33) |
Non-dense areac
| 1.12 (0.89,1.41) | 1.11 (0.88,1.39) | 9 % (p = 0.44) |
Selected risk factor | OR (95 % CI)
not adjusted for MD | OR (95 % CI) adjusted for MD | Percent mediated by MD (p value) |
---|---|---|---|
Childhood somatotypea
Per 1-unit increase | |||
Percent MDc
| 0.89 (0.83,0.96) | 0.92 (0.85,0.99) | 26 % (p = 0.01) |
Dense areac
| 0.89 (0.83,0.96) | 0.91 (0.84,0.98) | 16 % (p = 0.02) |
Non-dense areac
| 0.89 (0.83,0.96) | 0.90 (0.84,0.97) | 10 % (p = 0.10) |
Adolescent somatotypea
Per 1-unit increase | |||
Percent MDc
| 0.86 (0.80,0.93) | 0.90 (0.83,0.97) | 26 % (p = 0.01) |
Dense areac
| 0.86 (0.80,0.93) | 0.88 (0.81,0.95) | 13 % (p = 0.01) |
Non-dense areac
| 0.86 (0.80,0.93) | 0.88 (0.81,0.95) | 10 % (p = 0.13) |
BMI at age 18 (kg/m2)a
Per 5-unit increase | |||
Percent MDc
| 0.88 (0.74,1.05) | 1.00 (0.83,1.19) | 98 % (p = 0.17) |
Dense areac
| 0.88 (0.74,1.05) | 0.92 (0.77,1.10) | 35 % (p = 0.19) |
Non-dense areac
| 0.88 (0.74,1.05) | 0.94 (0.78,1.13) | 51 % (p = 0.24) |
Weight change since 18b
Per 20-lb increase | |||
Percent MDc
| 1.03 (0.96,1.10) | 1.11 (1.03,1.19) | Not mediatedd
|
Dense areac
| 1.03 (0.96,1.10) | 1.04 (0.97,1.12) | Not mediatedd
|
Non-dense areac
| 1.03 (0.96,1.10) | 1.10 (1.01,1.19) | Not mediatedd
|
BMI (kg/m2) Per 5-unit increase | |||
Percent MDc
| 1.05 (0.95,1.16) | 1.17 (1.05,1.30) | Not mediatedd
|
Dense areac
| 1.05 (0.95,1.16) | 1.07 (0.96,1.18) | Not mediatedd
|
Non-dense areac
| 1.05 (0.95,1.16) | 1.16 (1.02,1.30) | Not mediatedd
|
Height Per 3-inch increase | |||
Percent MDc
| 0.95 (0.85,1.06) | 0.96 (0.86,1.07) | 22 % (p = 0.41) |
Dense areac
| 0.95 (0.85,1.06) | 0.95 (0.85,1.06) | Not mediatedd
|
Non-dense areac
| 0.95 (0.85,1.06) | 0.96 (0.86,1.07) | 20 % (p = 0.39) |
Age at menarche Per 2-year increase | |||
Percent MDc
| 0.92 (0.80,1.05) | 0.93 (0.81,1.06) | 11 % (p = 0.37) |
Dense areac
| 0.92 (0.80,1.05) | 0.93 (0.81,1.06) | 13 % (p = 0.31) |
Non-dense areac
| 0.92 (0.80,1.05) | 0.92 (0.80,1.05) | Not mediatedd
|
Nulliparous Nulliparous vs parous | |||
Percent MDc
| 1.22 (0.88,1.69) | 1.12 (0.80,1.56) | 43 % (p = 0.26) |
Dense areac
| 1.22 (0.88,1.69) | 1.14 (0.82,1.59) | 32 % (p = 0.28) |
Non-dense areac
| 1.22 (0.88,1.69) | 1.19 (0.86,1.65) | 11 % (p = 0.36) |
Birth index Per 102-unit increase | |||
Percent MDc
| 0.96 (0.73,1.25) | 1.04 (0.79,1.36) | Not mediatede
|
Dense areac
| 0.96 (0.73,1.25) | 1.01 (0.78,1.33) | Not mediatede
|
Non-dense areac
| 0.96 (0.73,1.25) | 0.97 (0.74,1.27) | 38 % (p = 0.75) |
Parity (among parous) Per one-child increase | |||
Percent MDc
| 1.02 (0.95,1.09) | 1.03 (0.96,1.11) | Not mediatedd
|
Dense areac
| 1.02 (0.95,1.09) | 1.03 (0.96,1.10) | Not mediatedd
|
Non-dense areac
| 1.02 (0.95,1.09) | 1.02 (0.95,1.09) | Not mediatedd
|
Age at first birth (among parous) Per 5-year increase | |||
Percent MDc
| 1.23 (1.07,1.41) | 1.19 (1.04,1.38) | 13 % (p = 0.05) |
Dense areac
| 1.23 (1.07,1.41) | 1.20 (1.05,1.39) | 9 % (p = 0.09) |
Non-dense areac
| 1.23 (1.07,1.41) | 1.21 (1.05,1.40) | 5 % (p = 0.15) |
Breastfeeding (among parous) Ever vs never | |||
Percent MDc
| 0.96 (0.79,1.16) | 0.97 (0.80,1.17) | 22 % (p = 0.70) |
Dense areac
| 0.96 (0.79,1.16) | 0.96 (0.79,1.17) | 11 % (p = 0.74) |
Non-dense areac
| 0.96 (0.79,1.16) | 0.97 (0.80,1.17) | 19 % (p = 0.68) |
Breastfeeding (among parous women who ever breastfed) Per 12-month increase | |||
Percent MDc
| 1.25 (1.06,1.46) | 1.25 (1.06,1.47) | Not mediatedd
|
Dense areac
| 1.25 (1.06,1.46) | 1.24 (1.06,1.46) | 2 % (p = 0.57) |
Non-dense areac
| 1.25 (1.06,1.46) | 1.26 (1.07,1.48) | Not mediatedd
|
Alcohol use Per 10 g/day increase | |||
Percent MDc
| 1.01 (0.90,1.14) | 1.00 (0.89,1.13) | 73 % (p = 0.85) |
Dense areac
| 1.01 (0.90,1.14) | 1.01 (0.90,1.13) | 41 % (p = 0.85) |
Non-dense areac
| 1.01 (0.90,1.14) | 1.01 (0.90,1.13) | 38 % (p = 0.85) |
Family history of breast cancer Yes vs no | |||
Percent MDc
| 1.45 (1.15,1.85) | 1.45 (1.14,1.84) | 1 % (p = 0.78) |
Dense areac
| 1.45 (1.15,1.85) | 1.44 (1.14,1.84) | 2 % (p = 0.52) |
Non-dense areac
| 1.45 (1.15,1.85) | 1.46 (1.15,1.86) | Not mediatedd
|
History of biopsy-confirmed BBD Yes vs no | |||
Percent MDc
| 1.29 (1.04,1.61) | 1.19 (0.95,1.48) | 33 % (p = 0.04) |
Dense areac
| 1.29 (1.04,1.61) | 1.22 (0.98,1.52) | 24 % (p = 0.05) |
Non-dense areac
| 1.29 (1.04,1.61) | 1.27 (1.02,1.58) | 8 % (p = 0.12) |
History of unconfirmed BBD Yes vs no | |||
Percent MDc
| 1.19 (0.95,1.48) | 1.13 (0.90,1.41) | 29 % (p = 0.17) |
Dense areac
| 1.19 (0.95,1.48) | 1.13 (0.91,1.41) | 28 % (p = 0.17) |
Non-dense areac
| 1.19 (0.95,1.48) | 1.19 (0.95,1.48) | 0 % (p = 0.97) |
Age at menopause Per 4-year increase | |||
Percent MDc
| 1.12 (1.05,1.20) | 1.12 (1.04,1.19) | 5 % (p = 0.22) |
Dense areac
| 1.12 (1.05,1.20) | 1.12 (1.05,1.20) | 3 % (p = 0.30) |
Non-dense areac
| 1.12 (1.05,1.20) | 1.12 (1.05,1.20) | 3 % (p = 0.20) |
Hormone therapy use Past vs never | |||
Percent MDc
| 1.18 (0.91,1.53) | 1.12 (0.86,1.46) | 31 % (p = 0.26) |
Dense areac
| 1.18 (0.91,1.53) | 1.15 (0.88,1.50) | 14 % (p = 0.31) |
Non-dense areac
| 1.18 (0.91,1.53) | 1.15 (0.88,1.50) | 13 % (p = 0.31) |
Hormone therapy use Current vs never | |||
Percent MDc
| 1.71 (1.37,2.13) | 1.52 (1.22,1.90) | 22 % (p < 0.01) |
Dense areac
| 1.71 (1.37,2.13) | 1.58 (1.27,1.98) | 14 % (p < 0.01) |
Non-dense areac
| 1.71 (1.37,2.13) | 1.65 (1.32,2.05) | 7 % (p = 0.02) |