Table 1 Characteristics of breast cancer cases and matched controls, NHSII; mean ± SD or %.

Age at blood collection, y

45.0 ± 4.4

44.9 ± 4.4

Age at menarche, y

12.4 ± 1.3

12.4 ± 1.4

BMI at age 18, kg/m²

20.7 ± 2.9

21.1 ± 3.0

BMI at blood collection, kg/m²

25.5 ± 6.3

26.3 ± 7.1

Weight change since age 18, kg

11.6 ± 12.1

12.8 ± 13.8

Ever used oral contraceptives %

86

86

Duration of past oral contraceptives use, months*

47.4 ± 46.9

45.8 ± 45.6

Nulliparous, %

22

20

Parity, children^†

2.2 ± 0.9

2.3 ± 0.9

Age at first birth, y^†

26.6 ± 4.6

26.3 ± 4.6

Ever breast fed, %^†

78

80

Premenopausal at blood collection, %

77

76

Family history of breast cancer, %

17

10

History of benign breast disease, %

23

16

Plasma 25(OH)D level, ng/mL (nmol/L)

25.4 (63.4) ± 9.5 (23.7)

25.0 (62.4) ± 9.6 (24.0)

Time from blood collection to diagnosis, months

57.4 ± 33.5

NA