Impact of Metabolic Syndrome on Risk of Lung Cancer among Korean Never-Smokers: A Nationwide Population-Based Cohort Study

To determine the association between metabolic syndrome (MetS) and lung cancer risk in a large population-based cohort of never-smokers in Korea. Materials and MethodsUsing the Korean National Health Insurance Service database, we identified adults who underwent national health screening in 2009 and consistently reported their never-smoker status at baseline and subsequent examinations.Cox proportional hazards models were used to estimate hazard ratios (HRs) for lung cancer incidence, adjusting for age, sex, body mass index (BMI), physical activity, residential area, income, and alcohol consumption.Analyses were further stratified according to sex and BMI. ResultsOverall, 2,721,804 never-smokers were followed up for a mean of 14.0 years.The incidence of lung cancer was higher among participants with MetS than those without (adjusted HR: 1.04, 95% CI: 1.01-1.07).MetS was significantly associated with lung cancer risk in men (HR: 1.18, 95% CI 1.11-1.25)but not in women (HR: 1.03, 95% CI 0.99-1.07),with the risk evident in normal-weight and pre-obese men but, in women, mainly in those with obesity (HR: 1.10, 95% CI 1.03-1.16). ConclusionMetS was associated with a modest increase in the risk of lung cancer among Korean neversmokers, showing a significant association among men but not women.MetS risk was evident even among normal-weight men, whereas among women, it was more pronounced in those with obesity.These findings suggest that metabolic abnormalities, relatively underrecognized as cancer-related risk factors, could contribute to the risk of lung cancer, even in the absence of