Table 4b.
(2007–11) Relative risks (RRs) with 95% confidence intervals for invasive breast cancers among Danish women with complete reproductive information by reproductive variables (women born in 1935 or later), known ER±/HER2- expression and aged 50± years at the time of breast cancer diagnosis
| Exposure | ER+/HER2– <50 years | ER+/HER2– 50+ years | P-value for homogeneity ER+/HER2– 50± | ER–/HER2– <50 years | ER–/HER2– 50+ years | P-value for homogeneity ER–/HER2– 50± |
|---|---|---|---|---|---|---|
| Nulliparous cases (n = 1967) and parous cases (n = 15 597) | ||||||
| Number of cases | n = 1776 | n = 9670 | n = 468 | n = 1143 | ||
| Parity | RR | RR | RR | RR | ||
| Nulliparous | 1 | 1 | 1 | 1 | ||
| Parous | 1.03 (0.90, 1.18) | 0.90 (0.84, 0.96) | p = 0.10 | 1.36 (1.04, 1.77) | 1.03 (0.84, 1.26) | p = 0.09 |
| p-heterogeneity | 0.70 | 0.002 | 0.023 | 0.78 | ||
| Parous cases (n = 15 597) | ||||||
| Number of cases | n = 1527 | n = 8666 | n = 402 | n = 1037 | ||
| Live births | RR | RR | RR | RR | ||
| 1 | 1 | 1 | 1 | 1 | ||
| 2 | 1.01 (0.89, 1.15) | 0.94 (0.88, 0.99) | 1.03 (0.80, 1.32) | 1.13 (0.95, 1.36) | ||
| 3 | 0.96 (0.82, 1.14) | 0.91 (0.85, 0.97) | 0.79 (0.56, 1.11) | 1.08 (0.87, 1.33) | ||
| 4+ | 0.78 (0.58, 1.03) | 0.76 (0.68, 0.84) | P = 0.78 | 1.14 (0.70, 1.87) | 1.07 (0.80, 1.42) | P = 0.24 |
| p-trend | 0.27 | <0.001 | 0.52 | 0.79 | ||
| AFLB (years) | RR | RR | RR | RR | ||
| 12–19 | 0.95 (0.74, 1.21) | 1.01 (0.95, 1.08) | 1.14 (0.73, 1.78) | 1.21 (1.02, 1.42) | ||
| 20–24 | 1 | 1 | 1 | 1 | ||
| 25–29 | 1.16 (1.02, 1.32) | 1.06 (1.01, 1.12) | 0.99 (0.77, 1.27) | 1.07 (0.92, 1.24) | ||
| 30–34 | 1.48 (1.28, 1.72) | 1.25 (1.15, 1.35) | 1.22 (0.91, 1.63) | 1.04 (0.81, 1.34) | ||
| 35+ | 1.52 (1.22, 1.89) | 1.14 (1.00, 1.31) | <0.001 | 1.19 (0.75, 1.88) | 0.98 (0.63, 1.51) | P = 0.06 |
| p-trend | <0.001 | <0.001 | 0.42 | 0.21 | ||
| Nulliparous cases (n = 1967) and uniparous cases (n = 3011) | ||||||
| Number of cases | n = 579 | n = 2672 | n = 164 | n = 270 | ||
| AFLB (years) | RR | RR | RR | RR | ||
| 12–19 | 0.80 (0.41, 1.56) | 0.92 (0.77, 1.10) | 1.50 (0.47, 4.78) | 0.87 (0.50, 1.52) | ||
| 20–24 | 0.90 (0.66, 1.23) | 0.91 (0.82, 1.01) | 0.83 (0.41, 1.67) | 0.93 (0.67, 1.29) | ||
| 25–29 | 1.16 (0.92, 1.46) | 1.01 (0.91, 1.12) | 1.45 (0.95, 2.21) | 0.94 (0.67, 1.30) | ||
| 30–34 | 1.23 (0.98, 1.54) | 1.18 (1.04, 1.33) | 1.83 (1.23, 2.71) | 0.96 (0.64, 1.45) | ||
| 35+ | 1.17 (0.90, 1.53) | 1.08 (0.91, 1.27) | 1.14 (0.64, 2.06) | 0.98 (0.58, 1.67) | ||
| Nulliparous | 1 | 1 | P = 0.44 | 1 | 1 | P = 0.11 |
| p-trend | 0.86 | 0.13 | 0.15 | 0.52 | ||
Cases with unknown ER/HER2 status (n = 2304) were excluded from the ER/HER2-specific analyses. AFLB, age at first live birth.