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 | Â | Â | Â | Â |
   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 | Â | Â | Â | Â |
   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 |