Table 2.
Relative Risk of Breast Cancer According to Risk Factors Among Postmenopausal Women, Nurses’ Health Study, 1980–2010
| Breast Cancer Risk Factor | Invasive Breast Cancer (8,421 cases and 2,424,778 person-years) | ER+ Invasive Breast Cancer (5,376 cases and 2,421,194 person-years) | ER− Invasive Breast Cancer (1,270 cases and 2,416,662 person-years) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| RRa | 95% CI | P Valueb | RRa | 95% CI | P Valueb | RRa | 95% CI | P Valueb | |
| Nonmodifiable Risk Factors | |||||||||
| Age at menarche, years | <0.0001 | 0.003 | 0.13 | ||||||
| ≤12 | 1.17 | 1.11, 1.24 | 1.17 | 1.09, 1.26 | 1.11 | 0.96, 1.29 | |||
| 13 | 1.09 | 1.03, 1.16 | 1.12 | 1.03, 1.21 | 0.97 | 0.82, 1.14 | |||
| ≥14 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| BMI at age 18 yearsc | 0.0001 | 0.01 | 0.002 | ||||||
| <19.0 | 1.16 | 1.08, 1.25 | 1.10 | 1.00, 1.21 | 1.40 | 1.15, 1.70 | |||
| 19.0–20.9 | 1.18 | 1.11, 1.26 | 1.09 | 1.01, 1.19 | 1.46 | 1.22, 1.73 | |||
| 21.0–22.9 | 1.10 | 1.03, 1.18 | 1.05 | 0.97, 1.14 | 1.27 | 1.06, 1.51 | |||
| ≥23.0 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| Height, inchesd | <0.0001 | <0.0001 | 0.41 | ||||||
| <63.9 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| ≥64.0 | 1.12 | 1.07, 1.17 | 1.15 | 1.08, 1.22 | 1.05 | 0.93, 1.19 | |||
| Parity/age at first birth | <0.0001 | <0.0001 | 0.02 | ||||||
| Nulliparous | 1.23 | 1.12, 1.35 | 1.36 | 1.21, 1.52 | 1.03 | 0.80, 1.32 | |||
| ≥1 child, <25.0 years | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| 1–4 children, 25.0–29.9 years | 1.13 | 1.07, 1.19 | 1.13 | 1.06, 1.20 | 1.10 | 0.96, 1.25 | |||
| 1–4 children, ≥30.0 years | 1.34 | 1.24, 1.44 | 1.32 | 1.21, 1.45 | 1.33 | 1.10, 1.61 | |||
| >4 children | 1.06 | 0.96, 1.18 | 1.05 | 0.92, 1.19 | 1.13 | 0.88, 1.46 | |||
| Benign breast disease history | <0.0001 | <0.0001 | <0.0001 | ||||||
| No | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| Yes | 1.45 | 1.39, 1.51 | 1.40 | 1.33, 1.48 | 1.66 | 1.48, 1.86 | |||
| Family history of breast cancer | <0.0001 | <0.0001 | <0.0001 | ||||||
| No | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| Yes | 1.50 | 1.42, 1.51 | 1.58 | 1.48, 1.69 | 1.37 | 1.18, 1.59 | |||
| Age at menopause, years | <0.0001 | <0.0001 | 0.02 | ||||||
| <45.0 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| 45.0–51.9 | 1.24 | 1.17, 1.32 | 1.27 | 1.18, 1.36 | 1.26 | 1.09, 1.45 | |||
| ≥52.0 | 1.43 | 1.34, 1.53 | 1.49 | 1.37, 1.62 | 1.31 | 1.10, 1.55 | |||
| Modifiable Risk Factors | |||||||||
| Breastfeedinge | 0.07 | 0.24 | 0.30 | ||||||
| Never | 1.05 | 1.00, 1.10 | 0.96 | 0.91, 1.02 | 1.07 | 0.94, 1.21 | |||
| Ever | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| Weight change since age 18 years, kg | 0.13 | <0.0001 | 0.003 | ||||||
| Loss to 1.9-kg gain | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| 2.1- to 5.0-kg gain | 1.12 | 1.02, 1.24 | 1.21 | 1.07, 1.37 | 1.04 | 0.81, 1.33 | |||
| 5.1- to 10.0-kg gain | 1.21 | 1.11, 1.32 | 1.32 | 1.19, 1.47 | 1.16 | 0.94, 1.43 | |||
| 10.1- to 20.0-kg gain | 1.27 | 1.18, 1.37 | 1.37 | 1.25, 1.51 | 1.05 | 0.86, 1.27 | |||
| ≥20.1-kg gain | 1.50 | 1.39, 1.62 | 1.59 | 1.44, 1.75 | 1.38 | 1.13, 1.68 | |||
| Menopausal hormone use | <0.0001 | <0.0001 | 0.002 | ||||||
| Never or past user | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| Current user | 1.35 | 1.28, 1.42 | 1.43 | 1.34, 1.52 | 1.23 | 1.08, 1.40 | |||
| Alcohol consumptionf, g/day | <0.0001 | 0.0001 | 0.26 | ||||||
| 0 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
| 0.1–4.9 | 1.03 | 0.97, 1.09 | 1.02 | 0.94, 1.10 | 1.17 | 1.00, 1.37 | |||
| 5.0–15.0 | 1.13 | 1.05, 1.21 | 1.14 | 1.05, 1.24 | 1.18 | 0.99, 1.41 | |||
| >15.0 | 1.32 | 1.22, 1.42 | 1.37 | 1.25, 1.51 | 1.23 | 1.00, 1.51 | |||
| Quartile of physical activity, METs/week | 0.06 | 0.14 | 0.96 | ||||||
| 1 | 1.07 | 1.01, 1.15 | 1.08 | 0.99, 1.17 | 0.97 | 0.82, 1.15 | |||
| 2 | 1.05 | 0.98, 1.12 | 1.03 | 0.95, 1.11 | 0.96 | 0.82, 1.14 | |||
| 3 | 1.04 | 0.98, 1.11 | 1.05 | 0.97, 1.13 | 1.04 | 0.89, 1.22 | |||
| 4 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |||
Abbreviations: CI, confidence interval; ER−, estrogen receptor–negative; ER+ estrogen receptor–positive; METs, metabolic equivalent task hours; RR, relative risk.
a Model was adjusted for age in months, calendar year, and all other risk factors in table.
b The Wald P value is provided for nominal dichotomous variables and the P value for the linear trend is provided for ordinal variables. The P value for age at first birth by parity was obtained using a likelihood ratio test comparing models with and without the construct.
c Weight (kg)/height (m)2.
d One inch equals 2.54 cm.
e Among parous women.
f Cumulative average alcohol consumption.