Table 3.
Odds ratios (OR) and 95% confidence intervals (CI) for the association with breast density according to BMI group
| Characteristica | Current BMI | ||||
|---|---|---|---|---|---|
| <22.5 | 22.5–25.49 | 25.5–27.49 | 27.5–29.99 | ≥30 | |
| n = 35,547 | n = 37,153 | n = 18,744 | n = 18,775 | n = 33,799 | |
| OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | |
| Family history of breast cancer | |||||
| No | Reference | Reference | Reference | Reference | Reference |
| Yes | 1.09 (1.03, 1.14) | 1.03 (0.99, 1.08) | 1.08 (1.01, 1.15) | 1.15 (1.08, 1.23) | 1.09 (1.03, 1.15) |
| Age at menarche | |||||
| Overall OR (95% CI)b | 1.04 (1.03, 1.06) | 1.05 (1.03, 1.06) | 1.04 (1.02, 1.06) | 1.03 (1.01, 1.05) | 1.01 (0.99, 1.03) |
| p for trendb | <0.001 | 0.001 | 0.001 | 0.004 | 0.25 |
| <11 | Reference | Reference | Reference | Reference | Reference |
| 11 | 1.25 (1.09, 1.43) | 1.17 (1.05, 1.31) | 1.13 (0.98, 1.31) | 1.20 (1.05, 1.38) | 1.10 (0.99, 1.22) |
| 12 | 1.36 (1.20, 1.55) | 1.26 (1.13, 1.40) | 1.10 (0.96, 1.27) | 1.16 (1.01, 1.32) | 1.09 (0.98, 1.21) |
| 13 | 1.43 (1.26, 1.63) | 1.33 (1.20, 1.48) | 1.16 (1.01, 1.33) | 1.21 (1.06, 1.38) | 1.06 (0.94, 1.16) |
| 14 | 1.54 (1.34, 1.75) | 1.44 (1.28, 1.61) | 1.25 (1.08, 1.45) | 1.19 (1.02, 1.38) | 1.16 (1.02, 1.31) |
| 15+ | 1.52 (1.32, 1.75) | 1.43 (1.27, 1.61) | 1.26 (1.07, 1.48) | 1.33 (1.13, 1.56) | 1.06 (0.93, 1.21) |
| Age at first birthc | |||||
| Overall OR (95% CI)d | 1.08 (1.07, 1.09) | 1.07 (1.06, 1.08) | 1.07 (1.06, 1.09) | 1.06 (1.04, 1.07) | 1.03 (1.02, 1.04) |
| p for trendd | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| <20 | Reference | Reference | Reference | Reference | Reference |
| 20–24 | 1.21 (1.13, 1.31) | 1.20 (1.13, 1.28) | 1.15 (1.05, 1.26) | 1.13 (1.03, 1.23) | 1.04 (0.96, 1.11) |
| 25–29 | 1.39 (1.29, 1.51) | 1.34 (1.25, 1.44) | 1.21 (1.10, 1.34) | 1.31 (1.19, 1.45) | 1.10 (1.01, 1.19) |
| 30–34 | 1.45 (1.32, 1.60) | 1.55 (1.42, 1.70) | 1.40 (1.23, 1.59) | 1.42 (1.25, 1.63) | 1.11 (0.99, 1.24) |
| 35+ | 1.79 (1.56, 2.06) | 1.84 (1.61, 2.09) | 1.88 (1.56, 2.28) | 1.62 (1.33, 1.97) | 1.29 (1.08, 1.53) |
| Parity | |||||
| Overall OR (95% CI)d | 0.86 (0.85, 0.87) | 0.88 (0.87, 0.89) | 0.90 (0.88, 0.92) | 0.91 (0.89, 0.93) | 0.93 (0.92, 0.95) |
| p for trendd | <0.0001 | <0.0001 | <0.0001 | <0.0001 | <0.0001 |
| 0 | Reference | Reference | Reference | Reference | Reference |
| 1 | 0.75 (0.67, 0.84) | 0.80 (0.73, 0.89) | 0.93 (0.81, 1.08) | 1.13 (0.98, 1.30) | 0.95 (0.85, 1.07) |
| 2 | 0.61 (0.55, 0.66) | 0.67 (0.62, 0.73) | 0.74 (0.66, 0.84) | 0.90 (0.79, 1.02) | 0.85 (0.78, 0.94) |
| 3 | 0.52 (0.48, 0.58) | 0.58 (0.53, 0.63) | 0.68 (0.60, 0.77) | 0.80 (0.71, 0.91) | 0.81 (0.73, 0.89) |
| 4 | 0.44 (0.39, 0.48) | 0.52 (0.47, 0.57) | 0.60 (0.52, 0.69) | 0.71 (0.62, 0.81) | 0.75 (0.68, 0.84) |
| 5+ | 0.37 (0.34, 0.41) | 0.44 (0.40, 0.48) | 0.52 (0.45, 0.60) | 0.64 (0.56, 0.74) | 0.66 (0.59, 0.74) |
| Menopausal status | |||||
| Premenopausal | Reference | Reference | Reference | Reference | Reference |
| Postmenopausal | 0.67 (0.63, 0.72) | 0.68 (0.64, 0.72) | 0.71 (0.65, 0.77) | 0.73 (0.67, 0.79) | 0.75 (0.70, 0.80) |
| HT use | |||||
| No | Reference | Reference | Reference | Reference | Reference |
| Yes | 1.23 (1.15, 1.31) | 1.33 (1.26, 1.42) | 1.34 (1.23, 1.46) | 1.41 (1.30, 1.55) | 1.34 (1.25, 1.45) |
aAdjusted for age and current BMI as continuous variables
bBased on the cutpoints shown
cAmong parous women
dBased on the continuous form of the variable