Table 1 Characteristics of all study participants and stratified by BRCA1 mutation status

Age (years), mean (range)

38 (18–62)

34.4 (18–62)

43.6 (27–62)

0.007

Other white

34 (59 %)

20 (56 %)

14 (64 %)

0.04

Ashkenazi Jewish

10 (17 %)

3 (8 %)

7 (32 %)

Hispanic

3 (5 %)

3 (8 %)

0 (0 %)

East Asian

7 (12 %)

6 (17 %)

1 (4 %)

South Asian

4 (7 %)

4 (11 %)

0 (0 %)

Parous, ever, n (%)

29 (50 %)

12 (33.3 %)

17 (77.3 %)

0.003

Breastfeeding, ever, n (%)^a

23 (79 %)

10 (83 %)

13 (76 %)

1.00

Age at menarche (years), mean (SD)

12.4 (1.4)

12.2 (1.2)

12.7 (1.7)

0.20

Postmenopausal, n (%)

17 (29 %)

4 (11 %)

13 (59 %)

<0.001

Current oral contraceptive use, yes, n (%)

6 (10 %)

4 (11 %)

2 (9 %)

1.00

Current smoking status, yes, n (%)

1 (2 %)

0 (0 %)

1 (5 %)

0.40

Current alcohol consumption, yes, n (%)

51 (88 %)

31 (86 %)

20 (91 %)

0.70

Prophylactic bilateral mastectomy, yes, n (%)

9 (16 %)

0 (0 %)

9 (41 %)

<0.001

Prophylactic oophorectomy, yes, n (%)

14 (24 %)

1 (3 %)

13 (59 %)

<0.001

Current hormone replacement therapy, yes, n (%)

10 (17 %)

3 (8 %)

7 (32 %)

0.03

BMI, kg/m² (SD)

24.2 (5)

24.6 (5)

23.5 (4)

0.39

BRCA1 mRNA expression, mean (95 % CI)

164.3 (155, 173.5)

175.1 (163.4, 187)

146.7 (134.2, 159)

0.002