Table 1 Participant characteristics, including factors in the BWHS risk prediction model, by case–control status

First-degree family history of breast cancer

Age < 50 years

 No

275 (79.3)

575 (82.9)

 Relative diagnosed age ≥ 50 years

46 (13.3)

100 (14.4)

 Relative diagnosed age < 50 years or two relatives

26 (7.5)

19 (2.7)

Age ≥ 50 years

 No

416 (72.3)

924 (80.3)

 Relative diagnosed age ≥ 50 years

109 (19.0)

185 (16.1)

 Relative diagnosed age < 50 years or two relatives

50 (8.7)

41 (3.6)

First-degree family history of prostate cancer

 No

728 (79.0)

1509 (81.8)

 Yes

194 (21.0)

335 (18.2)

Age < 50 years

 Age at menarche < 14 years

295 (85.3)

551 (80.1)

 Age at menarche ≥ 14 years

51 (14.7)

137 (19.9)

Age ≥ 50 years

 Age at menarche < 14 years

483 (84.0)

887 (77.6)

 Age at menarche ≥ 14 years

92 (16.0)

256 (22.4)

Breastfeeding (parous women only)

 Never

382 (53.1)

840 (57.3)

 Ever

337 (46.9)

625 (42.7)

Oral contraceptive use

 Never or < 5 years

547 (59.3)

1266 (68.7)

 ≥ 5 years

375 (40.7)

578 (31.3)

Bilateral oophorectomy

 No

818 (88.7)

1625 (88.1)

 Yes

104 (11.3)

219 (11.9)

BMI at age 18 years, kg/m²

 < 25

830 (91.3)

1562 (86.3)

 ≥ 25

79 (8.7)

247 (13.7)

Premenopausal

 BMI < 30

206 (64.2)

423 (62.9)

 BMI ≥ 30

115 (35.8)

249 (37.1)

Postmenopausal

 BMI < 30

214 (57.1)

487 (58.7)

 BMI ≥ 30

161 (42.9)

342 (41.3)

Age < 50 years

 Never biopsy or benign breast disease

247 (71.2)

534 (76.9)

 Ever biopsy or benign breast disease

100 (28.8)

160 (23.1)

Age ≥ 50 years

 Never biopsy or benign breast disease

300 (52.2)

702 (61.0)

 Ever biopsy or benign breast disease

275 (47.8)

448 (39.0)

Mean age (SD)

52.7 (9.3)

52.7 (9.3)

Polygenic risk score, mean (SD)

0.23 (1.00)

− 0.12 (0.98)

BWHS 5-year breast cancer risk percent, mean (SD)

1.46 (0.67)

1.32 (0.57)