Table 2.
Relationship between baseline BMI and incidence of breast cancer among IBIS-I and IBIS-II postmenopausal participants
| BMI (kg/m2) | IBIS-I (N = 3731) | IBIS-II (N = 3750) | |||||
|---|---|---|---|---|---|---|---|
| N | Events (%) | HR (95% CI) | N | Events (%) | HR (95% CI) | ||
| Unadjusted | Continuous | 1.15 (1.04–1.27) | 1.21 (1.09–1.34)a | ||||
| < 25.0 | 1463 | 113 (7.7%) | Ref | 1140 | 64 (5.6) | Ref | |
| 25.0–29.9 | 1371 | 131 (9.6%) | 1.26 (0.98–1.62) | 1420 | 87 (6.1) | 1.12 (0.81–1.54) | |
| ≥ 30 | 896 | 90 (10.0%) | 1.34 (1.01–1.76) | 1190 | 97 (8.1) | 1.51 (1.10–2.07) | |
| Adjustedb | Continuous | 1.14 (1.03–1.26) | 1.20 (1.09–1.35) | ||||
| < 25.0 | Ref | Ref | |||||
| 25.0–29.9 | 1.23 (0.95–1.58) | 1.11 (0.80–1.54) | |||||
| ≥ 30 | 1.30 (0.98–1.71) | 1.51 (1.10–2.08) | |||||
Hazard ratios for continuous estimates are per 5 unit increase in baseline BMI
aIBIS-II analyses adjusted for IBIS-I participation
bAdjusted for age, HRT use, current or previous history of smoking, IBIS-I participation (IBIS-II analyses only) and menopausal status (IBIS-I analyses only)