Background:Xuanwei is one of the towns with highest lung
cancer mortality in China. Residents there frequently use smoky coal for domestic
cooking and heating. The smoking prevalence there is also
high.
Methods:We conducted a population-based case-control study. 388 lung cancer cases and 388 gender-age-area-matched controls
were surveyed. The exposure levels to potential lung cancer risk factors of
multi-aspects 10 years ago were collected. After checking Spearman
correlations between variables and referring to previous studies, we built
conditional logistic regression model adjusting education, family history of malignancy,
diet, alcohol consumption, occupational history, housing type and exposure to second
hand smoke. We then introduced household annual consumption of smoky coal and
total consumption of cigarettes from born to 10 years ago to the model in the
form of ordered categorical variable (coal level 1-3: never use, less than 3
tons per year, 3 tons or more per year; tobacco level 1-3: never use, less than
130 thousands cigarettes, 130 thousands or more cigarettes).
Results:There were 27% and 31.2% ever-smokers in case
and control group, respectively. Without interactive item, the effect of tobacco
use on lung cancer was (all comparing with level 1, with 95% confidence
intervals) level 2: OR=0.90(0.22, 3.67), level 3: OR=1.59(0.45, 5.70). After
adding interactive item of coal and tobacco in the model, the effect of tobacco
use among people never used smoky coal was level2: OR=1.09(0.09, 13.78),
level3: OR=2.20(0.16, 29.44); among people using relatively small amount of
coal was level2: OR=0.59(0.03, 11.37), level3: OR=0.18(0.01, 4.82); among
people using large amount of coal was level2: OR=0.93(0.32, 2.72), level3:
OR=1.78(0.30, 10.67).
Household annual amount of smoky coal used, 10 years ago | Total consumption of cigarettes from born to 10 years ago (reference group: never smoker) | β | SE | OR(95%CI) |
Never | <130000 cigarettes
≥130000 cigarettes | 0.0885
0.7863 | 1.2933
1.3245 | 1.09 (0.09, 13.78)
2.20 (0.16, 29.44) |
< 3 tons |
<130000 cigarettes
≥130000 cigarettes | -0.6172
-2.5037 | 1.9881
2.1385 | 0.59 (0.03, 11.37)
0.18 (0.01, 4.82) |
≥3 tons | <130000 cigarettes
≥130000 cigarettes | -0.1636
-0.2078 | 1.4050
1.6086 | 0.93 (0.32, 2.72)
1.78 (0.30, 10.67) |
[Table 1 Effect of tobacco use on lung cancer: diff]Conclusions:Tobacco use may lead to risk of lung cancer
among people never using smoky coal, and the effect increases according to
total amount of cigarettes consumption. Smoky coal use may negatively moderate
the relationship between tobacco and lung cancer.