Table 4 Cigarette smoking in relation to risk of rectal cancer by smoking and drinking status, Singapore Chinese Health Study, 1993-2004

From: Cigarettes and alcohol in relation to colorectal cancer: the Singapore Chinese Health Study

 

Former smokers

Current smokers

Nondrinkers

Drinkers

Cigarette smoking

No. of cases

HR (95% CI) a

No. of cases

HR (95% CI) a

No. of cases

HR (95% CI) a

No. of cases

HR (95% CI) a

Smoking status

 Never smokers

157

1.00

157

1.00

128

1.00

29

1.00

 Former smokers

63

1.35 (0.96–1.85)

—

—

47

1.72 (1.18–2.52)

16

0.91 (0.48–1.72)

 Current smokers

—

—

109

1.69 (1.26–2.25)

67

1.77 (1.27–2.48)

42

1.31 (0.79–2.19)

Number of cigarettes/day

 Never smokers

157

1.00

157

1.00

128

1.00

29

1.00

 <13

16

1.01 (0.59–1.72)

42

1.58 (1.10–2.27)

42

1.56 (1.07–2.26)

16

0.97 (0.52–1.82)

 13+

47

1.54 (1.06–2.24)

67

1.79 (1.28–2.50)

72

1.93 (1.37–2.73)

42

1.27 (0.76–2.12)

 P for trend

 

0.03

 

0.0004

 

0.0001

 

0.33

Age at starting to smoke

 Never smokers

157

1.00

157

1.00

128

1.00

29

1.00

 15+ years

46

1.16 (0.81–1.68)

80

1.55 (1.14–2.11)

87

1.63 (1.18–2.23)

39

0.97 (0.58–1.62)

 <15 years

17

2.36 (1.39–4.00)

29

2.33 (1.51–3.58)

27

2.38 (1.52–3.73)

19

2.08 (1.12–3.85)

 P for trend

 

0.0082

 

<0.0001

 

<0.0001

 

0.049

Number of years of smoking

 Never smokers

157

1.00

157

1.00

128

1.00

29

1.00

 <40 years

39

1.15 (0.78–1.69)

44

1.58 (1.09–2.29)

58

1.66 (1.17–2.36)

25

0.88 (0.50–1.54)

 40+ years

24

1.93 (1.20–3.09)

65

1.78 (1.27–2.50)

56

1.87 (1.30–2.70)

33

1.72 (0.97–3.05)

 P for trend

 

0.01

 

0.0004

 

0.0004

 

0.08

Smoking level b

 Never smokers

157

1.00

157

1.00

128

1.00

29

1.00

 Light Smokers

47

1.14 (0.79–1.65)

90

1.61 (1.19–2.17)

94

1.65 (1.21–2.25)

43

1.01 (0.61–1.67)

 Heavy smokers

16

2.97 (1.72–5.12)

19

2.38 (1.43–3.97)

20

2.73 (1.64–4.54)

15

2.30 (1.19–4.46)

 P for trend

 

0.0036

 

<0.0001

 

<0.0001

 

0.057

  1. aAll hazard ratios (HRs) were calculated using the Cox regression models that also included age, gender, dialect group, year of recruitment, level of education, body mass index, history of diabetes, family history of colorectal cancer, alcohol consumption (for both former and current smokers), and physical exercise (see details in the Method section).
  2. bHeavy smokers were those who started to smoke cigarettes before 15 years of age and smoked at least 13 cigarettes per day. Light smokers were those who started to smoke cigarettes at or after 15 years of age or smoked 12 or less cigarettes per day.
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