Table 2 Association between paternal and maternal ages at birth and risk of breast cancer in daughters

Paternal age

Mean ± SD

33.1 ± 7.5

32.5 ± 7.2

1.1 (1.00–1.28)^†

<30

362 (35.8)

400 (39.6)

1.0

1.0

30–34

266 (26.3)

261 (25.8)

1.2 (0.92–1.45)

1.0 (0.79–1.34)

35–39

169 (16.7)

174 (17.2)

1.1 (0.83–1.40)

1.0 (0.71–1.39)

≥40

214 (21.2)

176 (17.4)

1.4 (1.07–1.76)

1.6 (1.04–2.32)

P for trend

0.025

0.090

Maternal age

Mean ± SD

28.7 ± 6.4

28.3 ± 6.5

1.1 (0.97–1.28)^†

<25

285 (28.2)

330 (32.6)

1.0

1.0

25–29

302 (29.9)

297 (29.4)

1.2 (0.97–1.54)

1.2 (0.95–1.56)

30–34

237 (23.4)

192 (19.0)

1.5 (1.18–1.95)

1.4 (1.00–1.94)

≥35

187 (18.5)

192 (19.0)

1.1 (0.88–1.48)

0.8 (0.55–1.27)

P for trend

0.079

0.998