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Table 1 Baseline characteristics of invasive postmenopausal breast cancer cases and noncases in the Nurses' Health Study in 1980

From: Risk factors for ductal and lobular breast cancer: results from the nurses' health study

 

Noncases (n= 101,533)

All invasive cases (n= 6,226)

Ductal carcinoma (n= 4,655)

Lobular carcinoma (n= 659)

Reproductive or hormonal characteristics

    

   Mean age (yr)

53.7

54.5

54.5

54.4

   Mean age at menarche (yr)

12.7

12.6

12.6

12.5

   Mean parity among parous women

3.3

3.2

3.2

3.3

   Mean age at menopause (yr)a

48.7

49.5

49.4

49.7

   Ever used postmenopausal hormones (%)

47

48

50

51

   Natural menopause (%)

64

67

67

66

Nonreproductive characteristics

    

   Mean body mass index (kg/m2)

24.9

25.2

25.2

24.5

   Mean body mass index at age 18 (kg/m2)

21.4

21.0

21.0

21.2

   Median alcohol intake (g/day)

1.8

1.8

1.8

1.8

   Family history of breast cancer in first degree relative (%)b

8

13

14

11

   History of benign breast disease (%)

22

27

27

30

  1. aAmong those who experienced natural menopause. bFamily history in 1982.