INTRODUCTION Metabolic syndrome is known to increase the risk of several cancers. However, the association between lung cancer and metabolic syndrome remains unclear. Thus, we investigated the impact of metabolic syndrome on the incidence of lung cancer.

METHODS This study enrolled participants in a health screening program provided by the Korean National Health Insurance Service between January 2009 and December 2012. The incidence of lung cancer was observed until December 2016. We analyzed the risk of lung cancer according to the presence of metabolic syndrome, metabolic syndrome components, and number of metabolic syndrome components.

RESULTS During the study, 45 635 new cases of lung cancer were recorded among 9 586 753 participants. The presence of metabolic syndrome and all its components was positively associated with the risk of lung cancer in men after multivariate adjustment (hazard ratio [HR] of metabolic syndrome 1.15; 95% confidence interval [CI], 1.12-1.18). The risk of lung cancer increased with the number of components present. The effect of metabolic syndrome on the increasing risk of lung cancer is may be higher in underweight male ever-smokers than in other participants.

CONCLUSION Metabolic syndrome was associated with an increased risk of lung cancer in men. Moreover, the higher the number of metabolic syndrome components, the higher the risk of lung cancer.