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Table 2 Reproductive factors and risk of ER+PR+ and ER-PR- breast cancer in all women

From: Reproductive factors and risk of hormone receptor positive and negative breast cancer: a cohort study

 

Age and center stratified

Multivariable adjusted1

 

ER+PR+

ER-PR-

ER+PR+

ER-PR-

(n = 3567)

(n = 998)

(n = 3567)

(n = 998)

Reproductive factor

Cases

HR

95% CI

Cases

HR

95% CI

Cases

HR

95% CI

Cases

HR

95% CI

Age at menarche

<13 years

1373

1.00

Reference

376

1.00

Reference

1373

1.00

Reference

376

1.00

Reference

14 years

1717

0.96

(0.90-1.04)

481

0.98

(0.86-1.13)

1717

0.96

(0.89-1.03)

481

0.97

(0.85-1.12)

≥15 years

439

0.76

(0.68-0.85)

135

0.85

(0.69-1.04)

439

0.76

(0.68-0.85)

135

0.84

(0.69-1.03)

P for trend

  

<0.001

  

0.17

  

<0.001

  

0.17

Subtype heterogeneity2

     

0.44

     

0.48

Age at menopause 3

≤48 years

464

1.00

Reference

135

1.00

Reference

464

1.00

Reference

135

1.00

Reference

49–50 years

397

1.10

(0.95-1.26)

116

1.09

(0.84-1.41)

397

1.12

(0.98-1.29)

116

1.09

(0.84-1.42)

51–54 years

280

1.04

(0.89-1.21)

63

0.88

(0.64-1.20)

280

1.06

(0.91-1.24)

63

0.87

(0.64-1.20)

≥55 years

121

1.19

(0.97-1.47)

32

1.06

(0.71-1.58)

121

1.17

(0.95-1.44)

32

1.03

(0.69-1.54)

P for trend

  

0.18

  

0.79

  

0.18

  

0.79

Subtype heterogeneity2

     

0.40

     

0.34

Ever a full-term birth

No

446

1.00

Reference

115

1.00

Reference

446

1.00

Reference

115

1.00

Reference

Yes

2994

0.86

(0.77-0.95)

843

0.97

(0.80-1.19)

2994

0.87

(0.78-0.96)

843

0.98

(0.80-1.20)

P for significance

  

0.003

  

0.78

  

0.01

  

0.78

Subtype heterogeneity2

     

0.92

     

0.88

Number of full-term childbirths 4

1 child

612

1.00

Reference

160

1.00

Reference

612

1.00

Reference

160

1.00

Reference

2 children

1497

0.92

(0.84-1.01)

432

1.02

(0.85-1.22)

1497

0.92

(0.84-1.01)

432

1.01

(0.84-1.22)

>3 children

840

0.77

(0.69-0.85)

244

0.89

(0.72-1.09)

840

0.76

(0.68-0.85)

244

0.89

(0.73-1.10)

P for trend

  

<0.001

  

0.19

  

<0.001

  

0.19

Subtype heterogeneity2

     

0.22

     

0.20

Age at first full-term childbirth 4

≤19 years

357

1.00

Reference

103

1.00

Reference

357

1.00

Reference

103

1.00

Reference

20–24 years

1369

1.06

(0.94-1.20)

431

1.20

(0.97-1.50)

1369

1.07

(0.95-1.21)

431

1.20

(0.96-1.50)

25–29 years

912

1.20

(1.06-1.36)

242

1.16

(0.92-1.47)

912

1.22

(1.07-1.39)

242

1.17

(0.92-1.50)

30–34 years

275

1.35

(1.15-1.59)

61

1.10

(0.80-1.52)

275

1.39

(1.18-1.64)

61

1.12

(0.81-1.56)

≤35 years

82

1.44

(1.13-1.83)

14

0.91

(0.52-1.60)

82

1.47

(1.15-1.88)

14

0.93

(0.53-1.65)

P for trend

  

<0.001

  

0.96

  

<0.001

  

0.96

Subtype heterogeneity2

     

0.02

     

0.03

Time between menarche and first full-term childbirth 4

<10 years

837

1.00

Reference

257

1.00

Reference

837

1.00

Reference

257

1.00

Reference

≥10 years

2133

1.21

(1.12-1.31)

592

1.14

(0.98-1.32)

2133

1.22

(1.12-1.33)

592

1.15

(0.99-1.34)

P for significance

  

<0.001

  

0.09

  

<0.001

  

0.09

Subtype heterogeneity2

     

0.49

     

0.52

Age at last full-term childbirth 4

≤24 years

463

1.00

Reference

138

1.00

Reference

463

1.00

Reference

138

1.00

Reference

25–29 years

1058

0.98

(0.88-1.10)

321

1.01

(0.82-1.23)

1058

0.98

(0.88-1.10)

321

1.01

(0.82-1.23)

30–34 years

984

1.07

(0.95-1.20)

263

0.97

(0.78-1.19)

984

1.07

(0.96-1.20)

263

0.98

(0.79-1.21)

≥35 years

490

1.11

(0.97-1.26)

130

1.01

(0.79-1.29)

490

1.12

(0.98-1.28)

130

1.03

(0.80-1.33)

P for trend

  

0.03

  

0.90

  

0.02

  

0.90

Subtype heterogeneity2

     

0.24

     

0.29

Time since last full-term childbirth 4

≤20 years

1043

1.00

Reference

300

1.00

Reference

1043

1.00

Reference

300

1.00

Reference

>20 years

1952

0.87

(0.78-0.96)

552

1.00

(0.82-1.22)

1952

0.86

(0.77-0.95)

552

0.98

(0.81-1.20)

P for significance

  

0.01

  

0.98

  

0.01

  

0.98

Subtype heterogeneity2

     

0.20

     

0.24

Ever breast-fed 4

No

538

1.00

Reference

152

1.00

Reference

538

1.00

Reference

152

1.00

Reference

Yes

2317

0.99

(0.90-1.09)

642

0.97

(0.81-1.16)

2317

0.99

(0.89-1.09)

642

0.98

(0.81-1.17)

P for significance

  

0.82

  

0.74

  

0.76

  

0.74

Subtype heterogeneity2

     

0.85

     

0.93

Total cumulative breastfeeding duration 4,5

<1 month

249

1.00

Reference

72

1.00

Reference

249

1.00

Reference

72

1.00

Reference

1–3 months

602

1.04

(0.89-1.20)

155

0.91

(0.69-1.21)

602

1.04

(0.89-1.20)

155

0.91

(0.69-1.21)

4–6 months

460

0.97

(0.83-1.14)

137

0.98

(0.74-1.32)

460

0.97

(0.83-1.14)

137

0.99

(0.74-1.32)

7–12 months

487

0.97

(0.83-1.13)

132

0.91

(0.68-1.22)

487

0.97

(0.83-1.13)

132

0.91

(0.68-1.23)

13–17 months

182

0.91

(0.75-1.11)

62

1.10

(0.78-1.57)

182

0.92

(0.75-1.12)

62

1.12

(0.79-1.60)

≥18 months

293

1.09

(0.91-1.31)

77

1.04

(0.73-1.46)

293

1.11

(0.92-1.33)

77

1.07

(0.75-1.51)

P for trend

  

0.99

  

0.54

  

0.90

  

0.54

Subtype heterogeneity2

     

0.58

     

0.53

Ever an abortion 6

No

1552

1.00

Reference

435

1.00

Reference

1552

1.00

Reference

435

1.00

Reference

Yes

1016

1.00

(0.92-1.08)

293

1.00

(0.86-1.16)

1016

0.99

(0.91-1.07)

293

1.00

(0.86-1.16)

P for significance

  

0.97

  

0.98

  

0.72

  

0.98

Subtype heterogeneity2

     

0.97

     

0.86

OC use at recruitment

Never OC user

1477

1.00

Reference

379

1.00

Reference

1477

1.00

Reference

379

1.00

Reference

Past OC user

1839

1.00

(0.93-1.08)

548

1.11

(0.96-1.28)

1839

0.97

(0.90-1.05)

548

1.09

(0.94-1.26)

Current OC user

108

1.20

(0.97-1.47)

33

1.08

(0.73-1.59)

108

1.19

(0.96-1.47)

33

1.09

(0.74-1.63)

P for trend

  

0.42

  

0.20

  

0.95

  

0.20

Subtype heterogeneity7

     

0.34

     

0.30

Age started OC 8

≤24 years

899

1.00

Reference

292

1.00

Reference

899

1.00

Reference

292

1.00

Reference

25–29 years

335

0.86

(0.75-0.99)

94

0.86

(0.66-1.11)

335

0.87

(0.76-1.00)

94

0.86

(0.66-1.11)

30–34 years

303

0.91

(0.78-1.07)

90

0.92

(0.69-1.23)

303

0.93

(0.79-1.08)

90

0.92

(0.69-1.22)

≥35 years

265

1.07

(0.90-1.28)

73

0.97

(0.70-1.36)

265

1.09

(0.91-1.30)

73

0.97

(0.70-1.36)

P for trend

  

0.83

  

0.75

  

0.67

  

0.75

Subtype heterogeneity2

     

0.70

     

0.61

Duration of OC use 8

1 year or less

396

1.00

Reference

114

1.00

Reference

396

1.00

Reference

114

1.00

Reference

2–4 years

450

1.02

(0.89-1.17)

116

0.86

(0.66-1.12)

450

1.03

(0.89-1.18)

116

0.86

(0.67-1.12)

5–9 years

426

1.06

(0.92-1.22)

122

0.97

(0.75-1.26)

426

1.06

(0.92-1.22)

122

0.97

(0.75-1.27)

≥10 years

521

1.02

(0.89-1.17)

187

1.11

(0.87-1.41)

521

1.02

(0.89-1.18)

187

1.11

(0.87-1.42)

P for trend

  

0.70

  

0.21

  

0.68

  

0.21

Subtype heterogeneity2

     

0.36

     

0.37

  1. 1Stratified by age at recruitment and center and further adjusted for BMI, height, menopausal status at enrolment, HRT use, physical activity, smoking status, alcohol consumption and attained level of education; 2heterogeneity between ER+PR+ and ER-PR- tumors was assessed on the trend score using the data augmentation method as described by Lunn and McNeil; 3in postmenopausal women only; 4in parous women only; 5in women who breast-fed only; 6in both spontaneous and induced abortions; 7heterogeneity between ER+PR+ and ER-PR- tumors was assessed on the unordered categorical variable of never, past and current OC use using the data augmentation method as described by Lunn and McNeil; 8in women who ever used OC.
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