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Table 2 Relative risk of breast cancer in relation to smoking status, intensity, duration, dose, and cessation, by oestrogen receptor status

From: Smoking and risk of breast cancer in the Generations Study cohort

 

Oestrogen receptor status

All breast cancera

Positive

Negative

Cases

HRb

95% CI

P value

Cases

HRb

95% CI

P value

Cases

HRb

95% CI

P value

Ever previously smoked cigarettesc

 Never

898

1.00

Baseline

 

167

1.00

Baseline

 

1073

1.00

Baseline

 

 Ever

611

1.12

1.01–1.24

0.035

127

1.25

0.99–1.58

0.063

742

1.14

1.03–1.25

0.010

 

 Ever smoking by oestrogen receptor status interaction P = 0.40

Cigarettes per day, averaged over years when smokingd

 Never smoked

898

1.00

Baseline

 

167

1.00

Baseline

 

1073

1.00

Baseline

 

 1–4

216

1.07

0.92–1.25

0.36

41

1.11

0.79–1.56

0.54

258

1.08

0.94–1.24

0.29

 5–9

117

1.27

1.05–1.55

0.016

17

0.97

0.59–1.59

0.89

135

1.22

1.02–1.47

0.031

 10–14

68

1.37

1.07–1.76

0.013

13

1.34

0.76–2.36

0.31

82

1.37

1.09–1.72

0.0070

 15+

51

1.48

1.11–1.97

0.0079

11

1.61

0.87–2.97

0.13

62

1.48

1.14–1.92

0.0031

 Amount unknown

159

0.94

0.79–1.12

0.51

45

1.46

1.05–2.03

0.025

205

1.03

0.88–1.20

0.71

 

Trende P = 0.023

Trende P = 0.11

Trende P = 0.0060

Trend interaction P = 0.52

 

Duration of smoking, yearsf

 Never smoked

898

1.00

Baseline

 

167

1.00

Baseline

 

1073

1.00

Baseline

 

 1–9

139

0.95

0.79–1.13

0.57

37

1.30

0.91–1.85

0.15

177

1.00

0.85–1.18

0.97

 10–19

187

1.22

1.04–1.43

0.015

38

1.26

0.88–1.79

0.21

225

1.21

1.05–1.41

0.009

 20–29

113

1.16

0.95–1.41

0.15

28

1.59

1.06–2.38

0.025

141

1.21

1.02–1.45

0.033

 30+

137

1.23

1.03–1.48

0.024

20

1.07

0.67–1.71

0.78

159

1.22

1.02–1.44

0.026

 Duration unknown

35

0.97

0.69–1.36

0.86

4

0.61

0.23–1.66

0.34

40

0.93

0.68–1.28

0.66

 

Trende P = 0.17

Trende P = 0.85

Trende P = 0.24

Trend interaction P = 0.44

 

Pack-years of smokingd

 Never smoked

898

1.00

Baseline

 

167

1.00

Baseline

 

1073

1.00

Baseline

 

 1 to < 5

156

1.13

0.95–1.34

0.15

25

0.93

0.61–1.42

0.75

182

1.10

0.94–1.29

0.25

 5 to < 10

84

1.03

0.82–1.29

0.81

19

1.21

0.75–1.94

0.44

103

1.05

0.85–1.28

0.66

 10 to < 20

114

1.25

1.03–1.53

0.027

24

1.42

0.92–2.18

0.11

138

1.27

1.06–1.52

0.010

 20+

98

1.48

1.19–1.83

0.0003

14

1.22

0.71–2.13

0.47

114

1.45

1.19–1.77

0.0002

 Amount unknown

159

0.95

0.80–1.13

0.59

45

1.47

1.06–2.05

0.022

205

1.03

0.88–1.20

0.70

 

Trende P = 0.024

Trende P = 0.16

Trende P = 0.0069

Trend interaction P = 0.66

 

Current or former smokingc

 Never smoked

898

1.00

Baseline

 

167

1.00

Baseline

 

1073

1.00

Baseline

 

 Currentg

73

1.14

0.89–1.45

0.30

14

1.07

0.62–1.86

0.80

87

1.12

0.89–1.39

0.34

 Former

538

1.12

1.00–1.25

0.047

113

1.27

1.00–1.62

0.50

655

1.14

1.03–1.26

0.011

 

 Smoking status by oestrogen receptor status interaction P = 0.58

Time since cessation, yearsf

 Never smoked

898

1.00

Baseline

 

167

1.00

Baseline

 

1073

1.00

Baseline

 

 Currentg smoker

73

1.14

0.90–1.46

0.28

14

1.08

0.62–1.87

0.79

87

1.12

0.90–1.40

0.31

 1–9

100

1.25

1.01–1.54

0.040

26

1.48

0.98–2.23

0.064

127

1.28

1.06–1.55

0.009

 10–19

115

1.17

0.96–1.42

0.12

28

1.42

0.94–2.13

0.10

145

1.21

1.02–1.45

0.032

 20–29

133

1.10

0.91–1.32

0.33

20

0.94

0.59–1.51

0.81

153

1.07

0.90–1.27

0.46

 30+

170

1.05

0.88–1.24

0.61

38

1.43

0.99–2.06

0.058

209

1.10

0.94–1.28

0.24

 Duration unknown

20

1.06

0.68–1.65

0.81

1

0.29

0.04–2.08

0.22

21

0.93

0.60–1.43

0.74

 

Trende P = 0.055

Trende P = 0.85

Trende P = 0.071

Trend interaction P = 0.55

 
  1. aIncludes 12 breast cancers with unknown or unmeasured oestrogen receptor status
  2. bAdjusted for attained age (Cox regression time scale); time since recruitment to cohort (0, 1–2, 3+ years); birth cohort (1908–1939, 1940–1949, 1950–1959, 1960–1969, 1970–1996); benign breast disease (yes/no); family history of breast cancer in first-degree relatives (yes/no); socio-economic score (Acorn score as trend, missing); age at menarche (trend, missing); age at first pregnancy (trend, missing); parity (trend, missing); duration of breastfeeding (trend, missing); current oral contraceptive use before menopause (yes/no); alcohol consumption (never regular, trend current drinker 1 to < 60 g/day, current drinker ≥ 60 g/day, past drinker, drinker with unknown details); physical activity [log(metabolic equivalent) trend, missing]; pre-menopausal body mass index at age 20 years (trend, missing); post-menopausal body mass index (trend, missing); menopausal hormone therapy use (never used, ex-user, current oestrogen-only user, current oestrogen plus progestogen user, current user of other types, missing); menopausal status (pre- or post-menopausal) and age at menopause (trend, missing)
  3. cTime updated through follow-up period
  4. dTime updated at the point renewed information was available from follow-up questionnaire
  5. eTrend excludes never smoker and unknown group
  6. fTime updated in yearly steps
  7. gIncludes current smokers and < 1 year immediately after stopping
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Breast Cancer Research

ISSN: 1465-542X

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