Table 1 Characteristics of the study population

Age, years

48.3 ± 12.2

46.7 ± 20.8

54.6 ± 13.6

48.5 ± 17.7

Cohort (Komen/Yale)

0/34

45/5

0/79

44/47

Age groups

 < 50 years

21

27

32

44

 ≥ 50 years

13

23

47

47

Race/ethnicity

 Non-Hispanic White

23

45

62

79

 Hispanic White

3

2

3

4

 Africa American

4

3

7

6

 Others

4

0

7

2

Body mass index

26.6 ± 4.9

26.9 ± 5.3

28.2 ± 6.1

28.5 ± 6.7

Smoking

 Non-smoker

21

31

44

56

 Former smoker

12

14

30

25

 Current smoker

1

5

5

10

Alcohol consumption

 No

18

3

21

3

 Yes

16

47

58

88

Age at first birth

25.5 ± 5.6

25.8 ± 3.4

26.0 ± 5.0

26.2 ± 4.5

Menopause, yes

 No

24

25

35

37

 Yes

10

25

44

54

Age at menses onset

12.3 ± 1.7

12.5 ± 1.1

12.7 ± 1.7

12.4 ± 1.4

Number of birth

1.8 ± 1.4

2.2 ± 0.6

1.9 ± 1.4

2.1 ± 1.0

Total pregnancy

2.3 ± 1.9

2.5 ± 1.0

2.3 ± 1.9

2.6 ± 1.5

ER/PR

 +/+

23

 − 

49

 − 

 ±

1

 − 

2

 − 

−/−

1

 − 

10

 − 

Unknown

9

 − 

18

 − 

HER2

 Positive

3

 − 

4

 − 

 Negative

24

 − 

58

 − 

 Not typed/insufficient tissuee

7

 − 

10

 − 

 Unknown

0

 − 

7

 − 

BRCA testing

 Positive

2

 − 

2

0

 Negative

16

 − 

49

33

 Results unknown

6

 − 

12

0

 Not tested

10

 − 

16

9

Oral contraceptive pill use

 Current and former user

5

3

26

36

 Never

13

0

23

8

 Unknown

16

47

30

47

Ever hormone replacement therapy

 Yes

3

45

12

20

 No

3`

35

67

71