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Table 3 Association of reproductive characteristics with total cancer and breast cancer mortality in the EPIC study

From: Reproductive factors and risk of mortality in the European Prospective Investigation into Cancer and Nutrition; a cohort study

  

Total cancer (n = 5,938)

Breast cancer (n = 749)

ICD-10 code

 

C00–D48

C50

Variable

Value

Cases/ non-cases

HRa (95 % CI)

Cases / non-cases

HRa (95 % CI)

Parous

Yes

4,973 / 261,634

0.87 (0.80–0.93)

598 / 266,009

0.70 (0.58–0.85)

Number of FTPsb,c

1

944 / 47,240

1.00 (reference)

135 / 48,049

1.00 (reference)

 

2

2,164 / 125,284

0.91 (0.84–0.98)

268 / 127,180

0.74 (0.60–0.92)

 

3

1,069 / 57,773

0.89 (0.81–0.97)

119 / 58,723

0.70 (0.54–0.90)

 

4

442 / 16,880

1.05 (0.93–1.18)

55 / 24,591

0.68 (0.49–0.95)

 

5

118 / 4,680

0.86 (0.71–1.05)

  
 

≥6

88 / 2,438

1.11 (0.89–1.39)

  
 

P for trendd

0.85

 

0.012

Age at first FTP, yearsb

≤20

781 / 38,420

1.03 (0.94–1.14)

90 / 39,111

0.89 (0.68–1.16)

 

21–23

1,267 / 70,055

0.97 (0.90–1.05)

135 / 71,187

0.79 (0.63–0.99)

 

24–25

915 / 51,141

0.95 (0.87–1.03)

114 / 51,942

0.91 (0.72–1.15)

 

26–30

1446 / 74,481

1.00 (reference)

187 / 75,740

1.00 (reference)

 

≥31

531 / 26,496

1.06 (0.96–1.17)

70 / 26,957

1.05 (0.79–1.39)

Breastfeedinge

Ever

3,964 / 208,077

0.99 (0.91–1.08)

484 / 211,557

1.01 (0.79–1.29)

Breastfeeding, monthsf

≤1

399 / 20,571

1.00 (reference)

58 / 20,912

1.00 (reference)

 

>1 to ≤3

768 / 40,917

0.96 (0.85–1.09)

102 / 41,583

0.87 (0.62–1.21)

 

>3 to ≤6

783 / 42,744

0.92 (0.81–1.04)

82 / 43,445

0.68 (0.48–0.96)

 

>6 to ≤12

965 / 49,056

0.93 (0.83–1.05)

101 / 49,920

0.69 (0.49–0.97)

 

>12 to ≤18

434 / 23,868

0.87 (0.76–1.00)

63 / 24,239

0.88 (0.60–1.27)

 

>18

579 / 28,644

1.04 (0.90–1.19)

74 / 29,149

0.94 (0.65–1.37)

 

P for trendd

0.23

 

0.35

OC use in never or former

Never

2,376 / 104,288

1.00 (reference)

257 / 106,407

1.00 (reference)

smokers at baselineg

Ever

1,775 / 142,587

0.91 (0.85–0.98)

313 / 144,049

1.11 (0.91–1.35)

 

Formerh

1,656 / 124,219

0.91 (0.85–0.98)

291 / 125,584

1.12 (0.92–1.36)

 

Currenth

78 / 13,019

0.93 (0.73–1.20)

18 / 13,079

0.87 (0.50–1.50)

Duration of OC use, yearsg,i

≤1

325 / 25,843

1.00 (reference)

53 / 26,115

1.00 (reference)

 

>1 to <5

340 / 30,979

0.96 (0.82–1.12)

64 / 31,255

1.00 (0.69–1.45)

 

5 to <10

372 / 31,188

1.06 (0.91–1.23)

59 / 31,501

0.94 (0.64–1.37)

 

10 to <15

305 / 21,576

1.09 (0.92–1.28)

63 / 21,818

1.33 (0.91–1.94)

 

≥15

277 / 18,825

1.07 (0.90–1.27)

53 / 19,049

1.22 (0.81–1.83)

 

P for trendd

0.195

 

0.106

Age at menarche, years

<12

811 / 46,926

1.00 (reference)

98 / 47,639

1.00 (reference)

 

12

1,147 / 67,220

0.97 (0.89–1.06)

162 / 68,205

1.17 (0.91–1.51)

 

13

1,380 / 81,686

0.91 (0.83–0.99)

164 / 82,902

0.93 (0.72–1.20)

 

14

1,365 / 68,009

0.95 (0.87–1.04)

198 / 69,176

1.27 (0.99–1.63)

 

≥15

1,125 / 49,388

0.89 (0.81–0.98)

114 / 50,399

0.89 (0.67–1.18)

 

P for trendd

0.042

 

0.35

Age at natural menopause, yearsj

≤45

371 / 13,105

0.97 (0.86–1.10)

30 / 13,446

0.68 (0.45–1.03)

 

46–50

988 / 33,921

1.00 (reference)

120 / 34,789

1.00 (reference)

 

51–52

448 / 15,151

0.98 (0.88–1.10)

43 / 15,556

0.80 (0.56–1.14)

 

53–55

448 / 13,307

1.08 (0.96–1.21)

53 / 13,702

1.03 (0.73–1.45)

 

>55

141 / 3,483

1.12 (0.93–1.34)

13 / 3,611

0.87 (0.47–1.61)

 

P for trendd

0.080

 

0.37

  1. FTP, Full term pregnancy; OCs, Oral contraceptives; ICD-10, International Statistical Classification of Diseases Injuries and Causes of Death (10th revision)
  2. aCox regression adjusted for menopausal status (where applicable) (premenopausal [Ref], perimenopausal/unknown menopause, postmenopausal and surgical postmenopausal (bilateral oophorectomy)), body mass index (<23, 23–24.9 [Ref], 25–29.9, 30–39.9, 40+ kg/m2), physical activity index (inactive [Ref], moderately inactive, moderately active, active, unknown), education status (none/primary school [Ref], technical/professional school, secondary school/longer education including university, or unknown), smoking status/intensity (never [Ref], current 1–15 cigarettes/day, current 16–25 cigarettes/day, current 26+ cigarettes/day, former quit ≤10 years, former quit 11–20 years, former quit >20 years, current pipe/cigar/occasional smoker, current/former missing timing, unknown), smoking duration (<10 [Ref], 10 to <20, 20 to <30, 30 to <40, 40+ years, unknown), and stratified by age (continuous) and study centre
  3. bFTP includes live births and stillbirths
  4. cFor breast cancer the top categories were combined as indicated due to small numbers
  5. dP for trend values are based on continuous variables: the number of FTPs was modelled as 1 to ≥10; age at menarche as ≤8, 9–19, ≥20; age at menopause as <35, 35–60, >60
  6. eAmong parous women
  7. fAmong parous women who had ever breastfed (sum of all FTPs)
  8. gRestricted to participants who were never or former smokers, therefore models were adjusted for the same factorsa and a modified smoking status/intensity variable (never [Ref], former quit ≤10 years, former quit 11–20 years, former quit >20 years, former missing quit years, occasional smoker)
  9. hDoes not add up to the total number of OC users because 3.7 % of OC users were missing their timing of use
  10. iAmong ever users of OCs
  11. jAmong postmenopausal women; exclusions included participants from Sweden (no data for hysterectomy/oophorectomy), those who had a surgical menopause (hysterectomy and/or oophorectomy), or if information on surgical menopause was missing
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