Table 3 The relation for genetic risk score and established conventional risk factors with risk of breast cancer, The Singapore Chinese Health Study, 1993 to 1998

Genetic risk score, quartiles (range), mean

First (32.4-43.6), 40.4

80 (19.5)

326 (26.9)

1.00 (ref)

1.00 (ref)

1.00 (ref)

Second (43.6-47.1), 45.4

96 (23.4)

310 (25.6)

1.26 (0.90, 1.75)

0.178

1.25 (0.90, 1.75)

0.182

1.26 (0.90, 1.76)

0.174

Third (47.1-50.6), 48.9

109 (26.5)

296 (24.4)

1,47 (1.06, 2.04)

0.020

1.49 (1.07, 2.06)

0.017

1.47 (1.06, 2.04)

0.022

Fourth (50.6-65.8), 53.6

126 (30.7)

280 (23.1)

1.78 (1.29, 2.44)

<0.001

1.74 (1.26, 2.40)

0.001

1.75 (1.27, 2.41)

0.001

P trend

1.21 (1.09, 1.33)

<0.001

1.20 (1.09, 1.33)

<0.001

1.20 (1.08, 1.33)

<0.001

Age at first live birth, years

<20

56 (13.6)

212 (17.5)

1.00 (ref)

1.00 (ref)

1.00 (ref)

20-24

129 (31.4)

458 (37.8)

1.11 (0.77, 1.59)

0.571

1.04 (0.72, 1.50)

0.823

1.05 (0.73, 1.51)

0.804

25-29 or null

175 (42.6)

416 (34.3)

1.67 (1.16, 2.39)

0.005

1.51 (1.04, 2.18)

0.030

1.49 (1.03, 2.15)

0.036

≥30

51 (12.4)

126 (10.4)

1.62 (1.03, 2.55)

0.038

1.46 (0.92, 2.31)

0.111

1.49 (1.03, 2.29)

0.131

P trend

1.25 (1.09, 1.42)

0.001

1.20 (1.05, 1.38)

0.008

1.19 (1.04, 1.37)

0.011

Age at menarche, years

≥14

160 (38.9)

540 (44.6)

1.00 (ref)

1.00 (ref)

1.00 (ref)

12-13

180 (43.8)

484 (39.9)

1.29 (1.00, 1.66)

0.049

1.21 (0.93, 1.56)

0.151

1.23 (0.94, 1.60)

0.126

<12

71 (17.3)

188 (15.5)

1.34 (0.95, 1.89)

0.097

1.20 (0.84, 1.71)

0.312

1.19 (0.83, 1.71)

0.345

P trend

1.18 (1.00, 1.39)

0.048

1.12 (0.94, 1.32)

0.208

1.11 (0.94, 1.33)

0.220

Family history

No

400 (97.3)

1196 (98.7)

1.00 (ref)

1.00 (ref)

1.00 (ref)

Yes

11 (2.7)

16 (1.3)

2.11 (0.97, 4.61)

0.061

2.06 (0.94, 4.52)

0.071

1.78 (0.79, 4.00)

0.162

Past breast biopsy, n (%)

No

401 (97.6)

1193 (98.4)

1.00 (ref)

1.00 (ref)

1.00 (ref)

Yes

10 (2.4)

19 (1.6)

1.55 (0.69, 3.48)

0.288

1.36 (0.60, 3.08)

0.462

1.36 (0.58, 3.20)

0.475

Body mass index, kg/m²

<20

51 (12.4)

167 (13.8)

1.00 (ref)

1.00 (ref)

1.00 (ref)

20 to <24

216 (52.6)

659 (54.4)

1.09 (0.77, 1.54)

0.632

1.11 (0.78, 1.58)

0.562

1.16 (0.81, 1.66)

0.423

24 to <28

102 (24.8)

305 (25.2)

1.10 (0.75, 1.62)

0.610

1.12 (0.76, 1.64)

0.558

1.15 (0.78, 1.70)

0.488

28 or higher

42 (10.2)

81 (6.7)

1.74 (1.07, 2.85)

0.027

1.83 (1.12, 3.01)

0.016

1.99 (1.21, 3.29)

0.007

P trend

1.14 (0.99, 1.31)

0.067

1.15 (1.00, 1.33)

0.048

1.17 (1.02, 1.35)

0.031