Impact of smoking and smoking cessation on lung cancer mortality in the Asia-Pacific region.
Cigarette smoking is becoming increasingly common in Asia while quitting remains rare, in part because of a lack of knowledge about the risks of smoking. This study compared the risk of death from lung cancer associated with smoking habits in Australia and New Zealand and in Asia by using data from the Asia Pacific Cohort Studies Collaboration: 31 studies involving 480,125 individuals. Cox regression models were used. The hazard ratios for lung cancer mortality associated with current smoking were, for men, 2.48 (95% confidence interval (CI): 1.99, 3.11) in Asia versus 9.87 (95% CI: 6.04, 16.12) in Australia and New Zealand; p for homogeneity <0.0001. For women, the corresponding estimates were 2.35 (95% CI: 1.29, 4.28) in Asia versus 19.33 (95% CI: 10.0, 37.3) in Australia and New Zealand; p for homogeneity <0.0001. Quitting was beneficial in both regions; the hazard ratios for former compared with current smokers were 0.69 (95% CI: 0.53, 0.92) in Asia and 0.30 (95% CI: 0.22, 0.41) in Australia and New Zealand. The lesser effect in Asia was partly explained by the fewer number of cigarettes smoked and the shorter duration of follow-up in Asian studies. These results suggest that tobacco control policies in Asia should not solely concentrate on preventing the uptake of smoking but also attend to cessation.