Distribution of the 822 bp mtDNA deletion among cases and controls.

<p>Del, deletion. The median number of pack-years of combined cases and controls was utilized as the cut-point to stratify the cigarette smoking subjects. The single bar depicting the proportion of individuals who had the deletion or not. * indicating <i>p</i><0.001. (A) Distribution of the mtDNA deletion among subjects pooled from cases and controls and stratified by pack-years of cigarette smoking. Non-smokers who had no any history of cigarette smoking; Light-smokers who smoked 1–30 pack-years of smoking; Heavy-smokers who smoked >30 pack-years of smoking; <i>p</i> trend was calculated by the chi-square test for linear-by-linear association (both <i>p</i> value and <i>p</i> trend <0.001). (B) Distribution of the mtDNA deletion among light-cigarette and heavy-cigarette smoking subjects of combined cases and controls. Light-smokers who smoked 0–30 pack-years of smoking; Heavy-smokers who smoked >30 pack-years of smoking. ORs (95% CIs) and <i>p</i> value determined by multivariate logistic regression analysis, adjusted for age and gender (OR = 6.540, 95% CI = 3.247–13.174, adjusted <i>p</i> value<0.001). (C) Distribution of the mtDNA deletion among cases and controls. Compared with controls, the mtDNA deletion was significantly enriched in cases of lung cancer (<i>p</i><0.001). ORs (95% CIs) and <i>p</i> value determined by multivariate logistic regression analysis with adjustment for age, gender and smoking habits (OR = 3.776, 95% CI = 2.662–5.355, adjusted <i>p</i><0.001). (D) Distribution of the mtDNA deletion among non-cigarette smoking subjects pooled from cases and controls and stratified by gender. Non-smokers who had no any history of cigarette smoking. ORs (95% CIs) and <i>p</i> value determined by multivariate logistic regression analysis adjusted for age (OR = 5.814, 95% CI = 3.279–10.309, adjusted <i>p</i><0.001).