Table 3.
Odds ratios (ORs) and 95 % confidence intervals (95 % CIs) for breast cancer risk unadjusted and adjusted for mammographic density (MD) measures and percent of the association with breast cancer mediated by MD measures in women postmenopausal at mammogram in the NHS/NHSII (N = 731 cases/1695 controls)
| 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) |
Adjusted for age (continuous), fasting status (no, yes), time of blood collection (12 am–5:59 am, 6:00 am–7:59 am, 8:00 am–11:59 pm), mammography batch (NHS batch 1, NHS batch 2, NHSII), current BMI (continuous), BMI at age 18 (continuous), adolescent somatotype (continuous), history of biopsy-confirmed BBD (no, yes), history of unconfirmed BBD (no, yes), nulliparity (no, yes), parity (continuous), age at first birth (continuous, nulliparous set to median), age at menarche (continuous), and HT use (never, past, current). Percent of the total association (on the log odds scale) between the exposure and breast cancer risk that was mediated by MD was calculated using the following equation: 1-(lnORadjusted/lnORunadjusted)
BMI body mass index, BBD benign breast disease
aNot adjusted for adolescent somatotype, BMI at age 18, or current BMI
bNot adjusted for current BMI
cSquare-root transformed
dPercent mediated calculated to be <0 %
ePercent mediated calculated to be >100 %
Bold data in the header of column 2 in order to distinguish column 2 from column 3