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Table 2 Association between various reproductive and nonreproductive exposures and risk of postmenopausal breast cancer by histologic subtype among 107,759 women in the Nurses' Health Studya

From: Risk factors for ductal and lobular breast cancer: results from the nurses' health study

 

Ductal (n= 4,655)

Lobular (n= 659)

 

Reproductive or hormonal exposures

Cases (n)

RR (95% CI)

Cases (n)

RR (95% CI)

P-heterogeneityb

Age (per year)c

4,655

1.03 (1.03-1.04)

659

1.04 (1.03-1.06)

0.18

Age at menarche (per year)c

4,655

0.98 (0.96-1.00)

659

0.92 (0.87-0.97)

0.03

Parous

4,220

1.00 (ref)

610

1.00 (ref)

 

Nulliparous

437

1.26 (1.12-1.41)

49

1.22 (0.87-1.71)

0.87

Age at first birth (AFB)

     

   AFB < 25

2,354

1.00 (ref)

268

1.00 (ref)

 

   AFB 25-29

1,741

1.11 (2.04-1.19)

282

1.63 (1.37-1.96)

 

   AFB 30-34

425

1.21 (1.09-1.35)

86

2.31 (1.79-2.99)

 

   AFB ≥35

137

1.31 (1.10-1.57)

23

2.10 (1.35-3.26)

<0.001

   AFB, continuous, RR (P trend)c

 

1.12 (<0.001)

 

1.48 (<0.001)

<0.001

Parity

     

   Parity = 1

813

1.00 (ref)

100

1.00 (ref)

 

   Parity = 2

1,171

0.99 (0.91-1.07)

180

0.94 (0.76-1.16)

 

   Parity = 3

1,269

1.04 (0.96-1.13)

163

0.88 (0.71-1.09)

 

   Parity ≥ 4

1,404

0.91 (0.82-1.00)

216

0.96 (0.75-1.24)

0.35

   Parity, continuous, RR (P trend)d

 

0.97 (0.01)

 

1.05 (0.11)

0.02

Postmenopausal hormone use

     

   Never used

1,616

1.00 (ref)

181

1.00 (ref)

 

   Past use

1,165

1.05 (0.97-1.14)

150

1.11 (0.88-1.39)

 

   Current use, estrogen alone < 5 years

143

1.07 (0.90-1.28)

24

1.56 (1.01-2.42)

 

   Current use, estrogen plus progesterone < 5 years

283

1.56 (1.36-1.78)

42

2.16 (1.52-3.06)

 

   Current use, other ≤10 years

267

1.31 (1.15-1.49)

46

1.95 (1.40-2.71)

 

   Current use, estrogen alone 5-10 years

518

1.30 (1.17-1.45)

93

1.76 (1.34-2.34)

 

   Current use, estrogen + progesterone 5-10 years

463

1.75 (1.57-1.95)

99

3.12 (2.41-4.05)

<0.001

   Estrogen alone, continuous, RR (P trend)e

 

1.00 (0.008)

 

1.00 (0.24)

1.00

   Estrogen + progesterone, continuous, RR (P trend)e

 

1.02 (<0.001)

 

1.03 (<0.001)

0.43

   Other, continuous, RR (P trend)e

 

1.00 (0.45)

 

1.01 (0.30)

0.52

Age at menopause (per year)c

4,655

1.01 (1.00-1.01)

659

1.01 (1.00-1.02)

0.45

Menopausal type

     

   Natural or radiation-induced

2,958

1.00 (ref)

391

1.00 (ref)

 

   Surgical with two ovaries removed

667

0.80 (0.73-0.89)

101

1.00 (0.78-1.29)

 

   Surgical with one or no ovaries removed

559

0.87 (0.79-0.96)

100

1.21 (0.95-1.53)

0.08

Nonreproductive exposures

     

Body mass index (BMI)

     

   <21

473

1.00 (ref)

70

1.00 (ref)

 

   21 to less than 23

719

1.15 (1.02-1.29)

104

1.11 (0.82-1.50)

 

   23 to less than 25

858

1.21 (1.08-1.35)

122

1.14 (0.85-1.54)

 

   25 to less than 30

1,590

1.41 (1.27-1.57)

225

1.33 (1.01-1.75)

 

   ≥30

926

1.60 (1.42-1.80)

124

1.47 (1.08-2.00)

0.20

   BMI, continuous, RR (P trend)f

 

1.14 (<0.001)

 

1.12 (0.009)

0.75

BMI at age 18

     

   <19

839

1.07 (0.98-1.16)

114

1.00 (0.79-1.25)

 

   19 to less than 21

1,506

1.00 (ref)

221

1.00 (ref)

 

   21 to less than 23

959

0.83 (0.77-0.90)

148

0.88 (0.71-1.09)

 

   ≥23

744

0.74 (0.67-0.81)

99

0.69 (0.54-0.88)

0.16

   BMI at age 18, continuous, RR (P trend)f

 

0.77 (<0.001)

 

0.78 (0.003)

0.80

Alcohol intake (g/day)

     

   0

2,552

1.00 (ref)

334

1.00 (ref)

 

   <5

876

1.15 (1.06-1.24)

131

1.30 (1.05-1.59)

 

   5 to less than 15

765

1.22 (1.12-1.32)

113

1.34 (1.08-1.67)

 

   ≥15

462

1.31 (1.19-1.45)

81

1.75 (1.36-2.24)

0.20

   Alcohol intake, continuous, RR (P trend)g

 

1.04 (<0.001)

 

1.07 (<0.001)

0.11

Family history of breast cancer

     

   No

3,805

1.00 (ref)

544

1.00 (ref)

 

   Yes

850

1.55 (1.44-1.67)

115

1.41 (1.15-1.73)

0.39

Personal history of benign breast disease

     

   No

2,294

1.00 (ref)

298

1.00 (ref)

 

   Yes

2,361

1.47 (1.38-1.56)

361

1.60 (1.37-1.88)

0.32

  1. aEstimates adjusted for all variables presented in the table. bP value from likelihood ratio test comparing, for each covariate, the model with separate estimates for the ductal and lobular histologic subtypes to the model with a single estimate across the two subtypes. cRisk ratio (RR) for each 5-year increase in age among parous women. dRR for each child among parous women. eRR for each 5-year increase in use. fRR for each five-unit increase in BMI (kg/m2). gRR for each five-unit increase in daily alcohol consumption (g/day). 95% CI, 95% confidence interval.
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Breast Cancer Research

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