Pre-diagnostic leukocyte mitochondrial DNA copy number and risk of lung cancer

We prospectively investigated the relationship between mtCN and the risk of lung cancer in 463 case-control pairs from two prospective cohort studies, the Nurses' Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS). The adjusted least-squares means of log-transformed mtCN (log_mtCN) by smoking status were estimated by generalized linear models. Multivariable conditional logistic regression model adjusting for confounders was used to obtain the odds ratios (ORs) and 95% confidence intervals (CIs) for the association between log_mtCN and lung cancer risk. The adjusted least-squares mean of log_mtCN in heavy smokers was significantly lower than that in never smokers (P = 0.05). Compared to the high log_mtCN group, the risk of lung cancer was 1.29 (95% CI = 0.89-1.87) for the median group, and 1.11 (95% CI = 0.75-1.64) for the low group. Among current smokers, compared to participants with high levels of log_mtCN, those with median levels had a significantly higher risk of lung cancer (OR = 2.09; 95% CI = 1.12-3.90), but not those with low levels (OR = 1.37; 95% CI = 0.75-2.48). Further studies are warranted to confirm these findings.