Table 1 Selected risk factors at time of mammography by case-control status and menopausal status at the time of the mammogram (NHS/NHSII)

 Age^a

46.2 (4.6)

46.1 (4.3)

60.1 (7.0)

59.6 (7.4)

 Current BMI (kg/m²)

25.2 (4.8)

25.4 (5.1)

25.9 (4.6)

26.1 (5.0)

 Childhood somatotype

2.5 (1.2)

2.6 (1.2)

2.2 (1.2)

2.4 (1.3)

 Adolescent somatotype

2.8 (1.0)

2.9 (1.1)

2.5 (1.1)

2.7 (1.2)

 BMI at age 18 (kg/m²)

20.8 (2.5)

21.1 (2.7)

20.9 (2.4)

21.1 (2.7)

 Weight change since 18 (lbs)

26.7 (25.8)

26.3 (25.7)

29.7 (25.4)

29.7 (26.8)

 Age at menarche

12.3 (1.4)

12.4 (1.4)

12.5 (1.4)

12.6 (1.4)

 Parity (among parous)

2.4 (1.0)

2.5 (1.0)

3.2 (1.5)

3.2 (1.5)

 Age at first birth (among parous)

26.3 (4.4)

25.9 (4.1)

25.6 (3.7)

25.2 (3.5)

 Breastfeeding (months)

 (among parous women who ever breastfed)

16.3 (10.6)

17.1 (11.1)

12.6 (10.8)

11.4 (9.5)

 Birth index

46.0 (26.4)

46.7 (25.9)

56.4 (37.4)

55.8 (37.7)

 Height (inches)

65.1 (2.6)

64.9 (2.5)

64.5 (2.3)

64.6 (2.4)

 Alcohol use (g/day)

4.2 (6.9)

4.2 (6.3)

5.0 (7.5)

4.8 (7.8)

 Age at menopause (y)

47.8 (5.8)

46.7 (6.5)

 Percent density

46.1 (18.7)

39.7 (19.0)

29.2 (17.6)

24.8 (17.2)

 Dense area (cm²)

96.8 (57.5)

81.3 (50.8)

50.7 (38.4)

47.1 (38.9)

 Non-dense area (cm²)

121.4 (77.0)

134.4 (80.4)

141.3 (90.3)

157.5 (91.1)

 Nulliparous

81 (14.5)

228 (13.2)

65 (8.9)

139 (8.2)

 Ever breastfed (among parous)

361 (76.5)

1136 (76.9)

389 (53.6)

940 (55.8)

  Confirmed by biopsy

154 (27.5)

287 (16.6)

193 (26.4)

382 (22.5)

  Unconfirmed/unknown

170 (30.4)

566 (32.8)

190 (26.0)

423 (25.0)

 Family history of breast cancer

67 (12.0)

146 (8.5)

132 (18.1)

225 (13.3)

  Never

191 (26.1)

547 (32.3)

  Current

401 (54.9)

789 (46.5)

  Past

139 (19.0)

359 (21.2)