Table 3. Weight change since age 18 and incidence of breast cancer stratified by BMI at age 18, among premenopausal participants of the Nurses' Health Study. 1980-2008, and Nurses' Health Study II, 1993-2007 *.
| BMI at age 18 ≤ 21 kg/m2 | BMI at age 18 > 21 kg/m2 | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Weight change since age 18 (kg) | No. Of cases | Person-years | Age-adjusted | Covariate-adjusted | Covariate-adjusted controlling for weight at age 18 | No. of cases | Person-years | Age-adjusted | Covariate-adjusted | Covariate-adjusted controlling for weight at age 18 | ||||||
| HR | 95% CI | HR† | 95% CI | HR‡ | 95% CI | HR | 95% CI | HR† | 95% CI | HR‡ | 95% CI | |||||
| Lost ≥ 5 | 2‖ | 48 | 41,061 | 0.56 | (0.33, 0.96) | 0.54 | (0.31, 0.91) | 0.69 | (0.40, 1.18) | |||||||
| Lost 2 - 4.9 | 27 | 11,837 | 1.18 | (0.77, 1.82) | 1.16 | (0.75, 1.78) | 1.17 | (0.76, 1.80) | 36 | 31,764 | 0.86 | (0.54, 1.38) | 0.86 | (0.54, 1.36) | 0.90 | (0.58, 1.39) |
| Stable§ | 101 | 49,727 | 1.00 | 1.00 | 1.00 | 47 | 29,094 | 1.00 | 1.00 | 1.00 | ||||||
| Gained 2 - 4.9 | 161 | 88,559 | 0.90 | (0.70, 1.16) | 0.91 | (0.71, 1.17) | 0.90 | (0.70, 1.16) | 70 | 38,922 | 1.01 | (0.75, 1.36) | 1.02 | (0.76, 1.38) | 1.02 | (0.75, 1.37) |
| Gained 5 - 9.9 | 318 | 162,932 | 0.91 | (0.73, 1.15) | 0.91 | (0.72, 1.15) | 0.90 | (0.72, 1.14) | 124 | 69,916 | 0.88 | (0.66, 1.15) | 0.89 | (0.67, 1.17) | 0.87 | (0.66, 1.16) |
| Gained 10 - 14.9 | 227 | 110,814 | 0.89 | (070, 1.13) | 0.89 | (0.69, 1.13) | 0.87 | (0.68, 1.12) | 117 | 58,627 | 0.93 | (0.66, 1.30) | 0.93 | (0.65, 1.34) | 0.93 | (0.62, 1.40) |
| Gained 15 - 19.9 | 117 | 59,837 | 0.85 | (0.65, 1.12) | 0.86 | (0.65, 1.13) | 0.84 | (0.64, 1.12) | 63 | 45,096 | 0.76 | (0.55, 1.06) | 0.77 | (0.55, 1.07) | 0.77 | (0.55, 1.07) |
| Gained 20 - 24.9 | 63 | 34,844 | 0.80 | (0.49, 1.30) | 0.79 | (0.50, 1.26) | 0.78 | (0.50, 1.21) | 64 | 35,704 | 0.97 | (0.68, 1.37) | 0.95 | (0.67, 1.35) | 0.97 | (0.69, 1.38) |
| Gained ≥ 25 | 112 | 44,917 | 0.86 | (0.47, 1.56) | 0.83 | (0.41, 1.67) | 0.82 | (0.40, 1.68) | 114 | 80,283 | 0.67 | (0.48, 0.94) | 0.64 | (0.45, 0.91) | 0.68 | (0.48, 0.96) |
| p for trend in weight gain* | 0.72 | 0.70 | 0.68 | 0.003 | 0.004 | 0.02 | ||||||||||
*
Restricted to women who had stable weight or stable weight gain/loss since age 18 for at least two consecutive questionnaire cycles
†
Adjusted for age, family history of breast cancer, history of benign breast disease, height, age at menarche, age at first birth, parity, alcohol use, physical activity, current and past oral contraceptive use
‡
Additionally adjusted for weight at age 18 in kg (continuous)
§
Gain or loss up to 2 kg
‖
This stratum has too few cases to calculate a meaningful HR