COMBINED ANALYSIS OF CASE-CONTROL STUDIES OF SMOKING AND LUNG-CANCER IN CHINA

Fifteen case-control studies on the relationship between smoking and l ung cancers in China were analyzed and evaluated by the method of meta -analysis, using both the fixed-effect and the random-effect models. T he cumulative cases and controls were 5703 and 5669, respectively. Cal culations based on the fixed-effect model resulted in a combined odds ratio (OR) of 2.19, 95% CI, 2.03-2.73, with a population attributable risk (PAR) of 33.64%. A dose-response relationship between the amount of smoking, the duration of smoking (years), the age at which smoking started and the OR for developing lung cancer was found. The pooled OR for squamous cell carcinoma was 4.79, 95% CI, 4.02-5.70, with a PAR o f 65.44%. The combined OR for adenocarcinoma was 1.02, 95% CI, 0.87-1. 20, with a PAR of 0.99%. To further investigate the relationship betwe en smoking and lung cancer in Chinese women, twelve case-control studi es were analyzed by meta-analysis, using the fixed-effect model. The c umulative cases and controls were 2168 and 2496, respectively. The com bined OR was 2.19, 95% CI, 1.93-2.48, and the PAR was 30.34%. The comb ined OR for female squamous cell carcinoma was 7.35, 95% CI, 5.21-10.6 7, with a PAR of 53.97%. The combined OR for female adenocarcinoma was 1.09, 95% Cl, 0.82-1.94, with a PAR of 1.65%. The combined OR for exp osure to environmental tobacco smoke (E-TS) was 1.004, 95%, Cl, 0.74-1 .35 and the PAR was only 0.16%. The possible bias and confounding fact ors for this analysis are also discussed.