Dose-response relationship between the fatty liver index and asthma risk: NHANES 2001~2018

The correlation of obesity and metabolic abnormalities with asthma and non-alcoholic hepatic steatosis has been extensively studied. However, the association between asthma and non-alcoholic hepatic steatosis has been largely overlooked. This study aims to investigate the potential association between asthma risk and the fatty liver index (FLI), a validated indicator of non-alcoholic fatty liver disease (NAFLD). We screened 16,223 adults from National Health and Nutrition Examination Survey (NHANES) data between 2001 and 2018. Logistic regression analysis was performed to identify the association between FLI and asthma risk. We assessed their dose-response relationship using a restricted cubic spline (RCS) model. The threshold effect was analyzed to identify the FLI threshold point. Among the subjects screened, there were 2,192 cases suffered from asthma. After adjusting for all the confounders, using the Q3 group (FLI, 54-83) as the reference, the odds ratios (ORs) were 1.35 for the Q1 group (95% CI, 1.01-1.81), 1.21 for Q2 (95% CI, 0.98-1.49), and 1.48 for Q4 (95% CI, 1.27-1.73). Moreover, the RCS showed a nonlinear relationship between FLI and asthma risk (p < 0.05). Although the nonlinear relationship remained significant after gender-based stratification (p < 0.05), low FLI did not confer an increased risk of asthma in females. The optimal FLI threshold was 65 for the study sample; it was 68 and 63 for males and females, respectively (p < 0.05). This study demonstrated a nonlinear relationship between FLI and asthma risk. Furthermore, maintaining respective index values of 68 and 63 for males and females is likely associated with the lowest asthma risk.