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. 2010 Jul 20;103(5):727–729. doi: 10.1038/sj.bjc.6605791

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

      Before stove improvement
After stove improvement
   
Smoking variables n a Lung cancer deaths HRpre (95% CI) c P HRpost (95% CI) d P HRinteraction 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
  Ptrend       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

Abbreviations: CI=confidence interval; HR=hazard ratio.

a

Reduced data sets included exclusive smokers of each type and non-smokers.

b

HRinteraction=HRpost/HRpre.

c

Adjusted HR (95% CI) before stove improvement.

d

Adjusted HR (95% CI) after stove improvement. Significant results are shown in bold.