Table 2.
Multivariate-adjusted1 HRs (95% CI) for reproductive risk factors in relation to breast cancer subtypes in the Nurses' Health Studies
| Luminal A | Luminal B | HER2-enriched | Basal-like | Unclassified | All Subtypes | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| N, cases | 2063 | 1008 | 209 | 378 | 110 | 3768 | ||||||
| Age at menarche | ||||||||||||
| <12 years | 502 | 1 (ref.) | 246 | 1 (ref.) | 46 | 1 (ref.) | 96 | 1 (ref.) | 30 | 1 (ref.) | 920 | 1 (ref.) |
| 12 years | 608 | 0.95 (0.84, 1.07) | 257 | 0.84 (0.71, 1.00) | 59 | 0.95 (0.65, 1.41) | 93 | 0.79 (0.59, 1.05) | 30 | 0.76 (0.46, 1.27) | 1047 | 0.90 (0.82, 0.98) |
| 13 years | 593 | 0.80 (0.71, 0.90) | 313 | 0.92 (0.78, 1.09) | 60 | 0.83 (0.56, 1.23) | 112 | 0.86 (0.65, 1.13) | 31 | 0.65 (0.39, 1.09) | 1109 | 0.84 (0.76, 0.91) |
| 14 years | 205 | 0.67 (0.56, 0.79) | 126 | 0.94 (0.75, 1.17) | 26 | 0.80 (0.49, 1.31) | 50 | 0.94 (0.67, 1.34) | 10 | 0.50 (0.24, 1.04) | 417 | 0.77 (0.68,0.86) |
| > 14 years | 155 | 0.73 (0.61, 0.88) | 66 | 0.73 (0.55, 0.96) | 18 | 0.85 (0.49, 1.49) | 27 | 0.77 (0.50, 1.19) | 9 | 0.65 (0.30, 1.40) | 275 | 0.74 (0.65, 0.85) |
| P trend | <0.0001 | 0.13 | 0.33 | 0.21 | 0.06 | <0.0001 | ||||||
| P heterogeneity | 0.65 | |||||||||||
| Parity (ever/never) | ||||||||||||
| Nulliparous | 198 | 1 (ref.) | 104 | 1 (ref.) | 9 | 1 (ref.) | 34 | 1 (ref.) | 8 | 1 (ref.) | 353 | 1 (ref.) |
| Parous | 1865 | 0.89 (0.77, 1.04) | 904 | 0.84 (0.68, 1.04) | 200 | 2.01 (1.02, 3.97) | 344 | 1.05 (0.73, 1.51) | 102 | 0.96 (0.46, 2.00) | 3415 | 0.92 (0.82, 1.03) |
| P heterogeneity | 0.12 | |||||||||||
| Parity (categorical) 2 | ||||||||||||
| 1 child | 202 | 1 (ref.) | 105 | 1 (ref.) | 23 | 1 (ref.) | 34 | 1 (ref.) | 12 | 1 (ref.) | 376 | 1 (ref.) |
| 2 children | 603 | 0.97 (0.83, 1.15) | 286 | 0.81 (0.64, 1.02) | 62 | 0.88 (0.53, 1.46) | 108 | 1.06 (0.71, 1.58) | 30 | 0.77 (0.39, 1.56) | 1089 | 0.92 (0.82, 1.04) |
| 3 children | 550 | 1.05 (0.88, 1.25) | 263 | 0.86 (0.68, 1.11) | 48 | 0.78 (0.46, 1.35) | 105 | 1.29 (0.85, 1.96) | 31 | 0.86 (0.42, 1.78) | 997 | 0.99 (0.87, 1.13) |
| ≥4 children | 510 | 0.95 (0.79, 1.15) | 250 | 0.83 (0.64, 1.08) | 67 | 1.03 (0.59, 1.77) | 97 | 1.32 (0.84, 2.05) | 29 | 0.76 (0.36, 1.63) | 953 | 0.95 (0.83, 1.08) |
| P trend | 0.99 | 0.30 | 0.65 | 0.21 | 0.78 | 0.92 | ||||||
| P heterogeneity | 0.76 | |||||||||||
| Age at first birth 2 | ||||||||||||
| Per 1-year increase | 1.03 (1.02, 1.05) | 1.01 (0.99, 1.03) | 1.03 (0.99, 1.07) | 1.01 (0.98, 1.05) | 1.03 (0.97, 1.09) | 1.03 (1.02, 1.03) | ||||||
| P heterogeneity | 0.04 | |||||||||||
| Breastfeeding 2 | ||||||||||||
| Never | 607 | 1 (ref.) | 267 | 1 (ref.) | 62 | 1 (ref.) | 121 | 1 (ref.) | 29 | 1 (ref.) | 1086 | 1 (ref.) |
| ≤6 months or less | 504 | 0.83 (0.73, 0.93) | 265 | 1.00 (0.84, 1.19) | 50 | 0.79 (0.54, 1.15) | 88 | 0.76 (0.58, 1.01) | 32 | 1.09 (0.66, 1.81) | 939 | 0.86 (0.79, 0.94) |
| ≥7 months | 581 | 0.92 (0.81, 1.04) | 285 | 0.97 (0.81, 1.16) | 63 | 1.01 (0.69, 1.47) | 97 | 0.65 (0.49, 0.87) | 20 | 0.81 (0.45, 1.47) | 1046 | 0.90 (0.82, 0.99) |
| P trend | 0.99 | 0.81 | 0.10 | 0.02 | 0.47 | 0.58 | ||||||
| P heterogeneity | 0.27 | |||||||||||
| Age at menopause | ||||||||||||
| Per 1-year increase | 1.04 (1.02, 1.06) | 1.05 (1.03, 1.07) | 1.05 (1.00, 1.10) | 1.01 (0.98, 1.05) | 1.12 (1.04, 1.21) | 1.04 (1.03, 1.05) | ||||||
| P heterogeneity | 0.05 | |||||||||||
| Hormone therapy (HT) | ||||||||||||
| Never used HT | 1083 | 1 (ref.) | 492 | 1 (ref.) | 116 | 1 (ref.) | 215 | 1 (ref.) | 61 | 1 (ref.) | 1967 | 1 (ref.) |
| Past HT use | 237 | 0.90 (0.76, 1.05) | 150 | 1.07 (0.86, 1.34) | 36 | 0.94 (0.61, 1.44) | 47 | 1.20 (0.83, 1.75) | 14 | 1.42 (0.73, 2.75) | 484 | 0.99 (0.88, 1.11) |
| Current E-only use, <5 | 98 | 1.10 (0.89, 1.37) | 46 | 1.06 (0.77, 1.46) | 5 | 0.40 (0.16, 1.00) | 16 | 1.02 (0.59, 1.76) | 4 | 0.84 (0.29, 2.40) | 169 | 1.03 (0.87, 1.22) |
| Current E-only use, ≥5 | 182 | 1.35 (1.12, 1.62) | 110 | 1.37 (1.07, 1.76) | 14 | 0.71 (0.38, 1.32) | 30 | 1.44 (0.92, 2.27) | 12 | 3.16 (1.50, 6.67) | 348 | 1.35 (1.18, 1.55) |
| Current E+P use, <5 yrs | 144 | 1.67 (1.37, 2.02) | 70 | 1.47 (1.11, 1.96) | 11 | 0.83 (0.42, 1.62) | 11 | 0.83 (0.43. 1.59) | 5 | 1.33 (0.49, 3.63) | 241 | 1.48 (1.27, 1.72) |
| Current E+P use, ≥5 yrs | 96 | 2.09 (1.66, 2.65) | 72 | 1.85 (1.39, 2.46) | 11 | 1.48 (0.74, 2.95) | 13 | 1.96 (1.05, 3.65) | 2 | 1.93 (0.43, 8.75) | 194 | 1.97 (1.67, 2.32) |
| Current other use | 53 | 1.34 (1.01, 1.79) | 18 | 0.86 (0.53, 1.40) | 6 | 1.06 (0.45, 2.47) | 10 | 1.76 (0.90, 3.42) | 1 | 0.64 (0.09, 4.73) | 88 | 1.21 (0.97, 1.51) |
| P heterogeneity | 0.33 |
1
Mutually adjusted for all variables in table+ BMI at 18, weight change since 18, history of BBD, family history of breast cancer, total physical activity, alcohol intake, height, cohort
2
Among parous women only