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Table 2 Reproductive risk factors by study groupa

From: Risk factors for breast cancer in postmenopausal Caucasian and Chinese-Canadian women

 

Adjusted Mean (Lower and Upper 95% Confidence Limits)

    
    

P

 

Caucasians

Chinese born in the West or migrated to the West before 21

Recent Chinese migrants

P b

P c

P d

P e

 

(N = 413)

(N = 216)

(N = 421)

    

Age at menarche (years)f, g

12.8 (12.6, 13.0)

13.0 (12.7, 13.2)

13.7 (13.6, 13.9)

0.01

0.64

<0.001

<0.001

Age at first live birth (years)f, h

24.3 (23.8, 24.7)

24.9 (24.3, 25.5)

25.5 (25.1, 25.9)

0.002

0.34

<0.001

0.22

Number of live births (%)

       

0

14.5 (11.3, 18.5)

8.5 (5.2, 13.8)

4.5 (2.8, 7.2)

0.60

0.14

<0.001

0.19

1

9.9 (7.3, 13.2)

7.7 (4.6, 12.7)

18.0 (14.3, 22.4)

0.08

0.99

0.005

0.007

2

36.9 (32.3, 41.8)

40.1 (33.2, 47.4)

43.3 (38.5, 48.2)

0.14

0.99

0.22

0.99

3

21.6 (17.7, 26.1)

30.8 (24.7, 37.7)

19.6 (15.9, 37.7)

0.08

0.05

0.99

0.008

≥ 4

11.9 (8.9, 15.9)

5.3 (2.9, 9.6)

8.0 (5.7, 11.2)

0.33

0.05

0.24

0.71

Breastfeeding (% yes)

76.6 (71.6, 80.9)

63.4 (55.9, 70.2)

72.1 (66.9, 76.8)

<0.001

0.62

<0.001

0.14

Age at natural menopause (years)f, i

50.1 (49.7, 50.6)

50.6 (50.0, 51.3)

49.9 (49.5, 50.3)

0.79

0.53

0.99

0.10

Age at surgical menopause with both ovaries removed (years)f, j

44.0 (41.2, 46.9)

45.0 (41.3, 48.9)

45.0 (42.2, 48.0)

0.68

0.99

0.99

0.99

Ever used oral contraceptives (% yes)

85.8 (81.4, 89.3)

73.9 (67.3, 79.6)

40.7 (35.9, 45.7)

<0.001

0.002

<0.001

<0.001

Duration of oral contraceptive use (years)f, k

3.6 (3.0, 4.3)

2.5 (2.0, 3.2)

2.1 (1.7, 2.6)

0.14

0.03

<0.001

0.81

Ever used hormone replacement therapy (% yes)

47.4 (41.7, 53.1)

33.1 (26.6, 40.3)

28.1 (23.9, 32.6)

0.03

0.003

<0.001

0.65

Duration of hormone replacement therapy use (years)f, l

2.1 (1.6, 2.8)

1.7 (1.2, 2.6)

1.1 (0.8, 1.4)

0.01

0.99

0.001

0.17

  1. a P values were based on ANCOVA for continuous variables and logistic regression for binary variables, adjusting for age, education, and age × ethnicity. Pairwise comparisons were adjusted for multiple comparisons using the Bonferroni method. Variables are expressed as adjusted means.
  2. b P values for ethnicity effect.
  3. c P values for comparing Caucasians and Chinese born in the West or migrated to the West before age 21.
  4. d P values for comparing Caucasians and recent Chinese migrants.
  5. e P values for comparing Chinese born in the West or migrated to the West before age 21 and recent Chinese migrants.
  6. f Log transformed.
  7. g There were 3 missing values for Chinese born in the West or migrated to the West before age 21 and 2 missing values for recent Chinese migrants.
  8. h Sample size was 344 Caucasians, 191 Chinese born in the West or migrated to the West before age 21, and 397 recent Chinese migrants.
  9. i Sample size was 274 Caucasians, 159 Chinese born in the West or migrated to the West before age 21, and 345 recent Chinese migrants.
  10. j Sample size was 28 Caucasians, 13 Chinese born in the West or migrated to the West before 21, and 24 recent Chinese migrants.
  11. k Sample size of oral contraceptive uses was 313 Caucasians, 154 Chinese born in the West or migrated to the West before 21, and 169 for recent Chinese migrants.
  12. l Sample size of hormone replacement therapy users was 201 Caucasians, 68 Chinese born in the West or migrated to the West before 21, and 118 recent Chinese migrants.
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Breast Cancer Research

ISSN: 1465-542X

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