Table 2 Effects of smoking on lung cancer mortality before and after stove improvement in Xuanwei, 1976–1996

From: Differential effects of smoking on lung cancer mortality before and after household stove improvement in Xuanwei, China

   

Before stove improvement

After stove improvement

  

Smoking variables

n a

Lung cancer deaths

HR pre (95% CI) c

P

HR post (95% CI) d

P

HR interaction b

P interaction

Duration of smoking of any type

 Duration (per year)

21 686

 

0.995 (0.987–1.002)

0.17

1.009 (1.002–1.017)

0.02

1.015

0.002

<20

2949

188

1.00 (Ref.)

 

1.00 (Ref.)

 

1.00

 

⩾20–<30

6971

270

0.81 (0.61–1.07)

0.14

1.02 (0.77–1.37)

0.88

1.26

0.23

⩾30–<40

5906

434

0.92 (0.69–1.22)

0.57

1.39 (1.05–1.86)

0.03

1.51

0.02

⩾40

5860

341

1.05 (0.75–1.46)

0.79

1.70 (1.23–2.34)

0.001

1.62

0.01

P trend

   

0.85

 

0.0008

 

0.005

Smoking type (pack-years)

 Cigarettes (per pack-year)

6394

333

0.997 (0.985–1.009)

0.61

1.015 (1.005–1.025)

0.0004

1.018

0.02

Unfiltered

5637

292

0.990 (0.976–1.004)

0.15

1.013 (1.002–1.025)

0.03

1.024

0.009

Filtered

2018

41

1.014 (0.984–1.045)

0.37

1.019 (0.997–1.042)

0.09

1.005

0.77

 Chinese long-stem pipe (per (20 g day–1)*year)

8075

635

0.996 (0.991–1.002)

0.20

1.000 (0.996–1.005)

0.92

1.004

0.25

 Water pipe (per (20 g day–1)*year)

2092

112

1.004 (0.987–1.022)

0.61

1.007 (0.987–1.028)

0.48

1.003

0.83

  1. Abbreviations: CI=confidence interval; HR=hazard ratio.
  2. aReduced data sets included exclusive smokers of each type and non-smokers.
  3. bHRinteraction=HRpost/HRpre.
  4. cAdjusted HR (95% CI) before stove improvement.
  5. dAdjusted HR (95% CI) after stove improvement. Significant results are shown in bold.
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