Skip to main content

Table 1 Baseline characteristics of the participants by status in the UK and Norwegian studiesa

From: Adjusting for BMI in analyses of volumetric mammographic density and breast cancer risk

UK case control study

Norwegian cohort study

 

Controls (n = 685)

Cases (n = 414)

Non-cases

(n = 61,059)

Cases

(n = 657)

Age at mammography

 Mean (SD)

59.5 (6.6)

67.5 (12.7)

56.9 (5.74)

57.7 (5.43)

 Number

679

412

61,059

657

BMIb

 Mean (SD)

26.1 (5.6)

26.4 (4.9)

25.6 (4.2)

25.8 (4.1)

 Number

656

368

54,345

589

Ethnicity (UK)/Country of birth (Norway), n (%)

 White/Norway

520 (76.5)

370 (89.4)

56,234 (93.8)

612 (94.2)

 Non-white/Outside Norway

160 (23.5)

39 (9.6)

3693 (6.2)

38 (5.8)

 Missing

5

5

1132

7

Family history of BC, n (%)

 No

N/A

N/A

45,168 (77.1)

447 (70.0)

 Yes

N/A

N/A

13,390 (22.9)

192 (30.0)

 Missing

  

2501

18

Menopausal statusc, n (%)

 Pre- + peri-menopausal

91 (13.3)

55 (13.3)

14,776 (25.2)

141 (22.1)

 Post-menopausal

591 (86.7)

358 (86.7)

43,856 (74.8)

496 (77.9)

 Missing

3

1

2427

20

Parity, n (%)

 Nulliparous

209 (30.9)

65 (15.9)

4946 (8.5)

57 (9.0)

 Parous

467 (69.1)

343 (84.1)

53,563 (91.5)

577 (91.0)

 Missing

9

6

2550

23

Age at menarche in years, n (%)

  <13

271 (53.9)

159 (54.1)

16,764 (40.9)

186 (41.9)

 14+

232 (46.1)

135 (45.9)

24,202 (59.1)

258 (58.1)

 Missing

14

33

4107

43

Hormone therapy use, n (%)

 No

459 (68.8)

246 (63.2)

34,150 (66.2)

305 (55.6)

 Yes

208 (31.2)

143 (36.8)

17,418 (33.8)

244 (44.4)

 Missing

18

25

9491

108

Educational level, n (%)

 None/primary school

35 (5.2)

17 (6.2)

  

 Lower secondary

  

13,772 (23.3)

164 (25.9)

 Secondary or higher

641 (94.8)

225 (93.8)

45,457 (76.7)

470 (74.1)

 Missing

9

142

1830

23

Breastfeeding among parous women, n (%)

 Yes

358 (76.7)

224 (74.7)

46,107 (99.9)

497 (100)

 Missing

3

43

9929

103

  1. Abbreviations: BC breast cancer, BMI body mass index, N/A data not available, SD standard deviation
  2. aPercentages calculated without missing values
  3. bBMI estimated from self-reported height and weight as weight/height2 (in kg/m2)
  4. cPost-menopausal women defined as those who self-reported natural (cessation of menses for at least 12 months) or surgical menopause, were older than 55 years, or had ever used hormone therapy. Owing to small numbers, pre-menopausal (younger than 55 years and still having regular periods) and peri-menopausal (younger than 55 years and having irregular periods) women were combined into a single category