Association between body-mass index change and lung cancer risk in Korea: nested case-control study

Previous studies have demonstrated an association between body mass index (BMI) and lung cancer risk, while additional research has found that BMI change affects lung disease. This study aims to investigate the association between BMI changes with lung cancer risk in Korea. We identified 18,941 patients diagnosed with lung cancer for the first time between 2018 and 2022 using the Korean National Health Insurance claims database. A nested case-control design was applied with 1:5 age, sex and year matching, resulting in 94,705 controls. BMI change variables included the magnitude of change in BMI, rates, and groups of rates. Odds ratios for cancer risk were estimated using conditional logistic regression, adjusted for covariates. Subgroup analyses were conducted based on obesity classification and smoking status. Of 113,646 individuals (87,912 [77.4%] male), underweight individuals had a higher risk (OR, 1.22; 95% CI, 1.10–1.34) compared to normal-weight individuals, whereas overweight (OR, 0.91; 95% CI, 0.88–0.95) and obese (OR, 0.83; 95% CI, 0.80–0.86) individuals showed reduced risk. A decrease in BMI was associated with increased lung cancer risk (OR, 0.97; 95% CI, 0.96–0.98), particularly among normal-weight (OR, 0.96, 95% CI: 0.94–0.99) and obese (OR, 0.96, 95% CI, 0.94–0.99) individuals. The impact of BMI decrease on lung cancer risk was most pronounced among current smokers, followed by ex-smokers and non-smokers. The association between BMI change and lung cancer risk was confirmed. As a predictive factor, BMI change could be assessed during health examinations as an indicator for cancer screening.