Nonalcoholic Fatty Liver Disease Increases the Risk of Lung Abscess: Findings from a Nationwide Cohort Study

<b>Objectives:</b> This study aimed to investigate the association between nonalcoholic fatty liver disease (NAFLD), assessed by the Fatty Liver Index (FLI), and the occurrence of lung abscess within a large population-based cohort. <b>Method:</b> We conducted a nationwide retrospective study using data from 367,930 subjects who underwent National Health check-ups between 2009 and 2018. Cox proportional hazards regression was performed to evaluate the association between the FLI and the incidence of lung abscess and community-acquired pneumonia (CAP) after adjusting for age, sex, and relevant covariates. <b>Results:</b> Among the study population, 455 (0.12%) and 44,934 (12.2%) patients were diagnosed with lung abscesses and CAP, respectively. The cumulative incidence of lung abscess was higher in individuals with elevated FLI values (FLI < 30, 0.10%; 30 ≤ FLI < 60, 0.16%; FLI ≥ 60, 0.18%; <i>p</i> < 0.001), whereas the incidence of CAP decreased across FLI groups (FLI < 30, 12.4%; 30 ≤ FLI < 60, 12.3%; FLI ≥ 60, 11.0%; <i>p</i> < 0.001). After adjusting for covariates, the risk of lung abscess significantly increased in the 30 ≤ FLI < 60 (Hazard ratio (HR) = 1.26; 95% confidence interval (CI), 0.95-1.68; <i>p</i> = 0.115) and the FLI ≥ 60 (HR = 1.67; 95% CI, 1.37-2.29; <i>p</i> < 0.001) groups, although the risk of CAP was relatively small in both groups (30 ≤ FLI < 60; HR = 1.06; 95% CI, 1.03-1.09; <i>p</i> < 0.001) (FLI ≥ 60; HR = 1.13; 95% CI, 1.08-1.12; <i>p</i> < 0.001). <b>Conclusions:</b> Our study provides compelling evidence supporting a potential link between NAFLD, as measured by FLI, and the incidence of lung abscess. These findings suggest the importance of vigilant monitoring of respiratory health in patients with NAFLD and emphasise the need for early detection of possible complications.