Association of serum osmolality with metabolic dysfunction-associated steatotic liver disease in adults.

PURPOSE: Hydration status is linked to metabolic syndrome, hypertension, and obesity in adults, and dehydration is associated with metabolic dysfunction-associated steatotic liver disease (MASLD) in children. However, the relationship between serum osmolality (OSM) and MASLD odds in adults remains unclear. METHODS: This cross-sectional study analyzed NHANES data (2017-March 2020). MASLD was defined as hepatic steatosis (controlled attenuation parameter >248 dB/m) plus at least one metabolic risk factor. Serum OSM was calculated using the ESPEN-recommended equation. Restricted cubic spline (RCS) and weighted logistic regression analyses were performed, adjusting for age, sex, poverty-income ratio (PIR), race, smoking, drinking, energy intake, and physical activity. Subgroup analyses were conducted to enhance the robustness of the results. RESULTS: Among 3,799 participants, higher serum OSM (Q4 vs. Q1) was associated with increased odds of MASLD in unadjusted (OR=2.02, 95% CI 1.29-3.16), partially adjusted (OR=1.64, 95% CI 1.08-2.49), and fully adjusted models (OR=1.60, 95% CI 1.02-2.50). RCS analysis revealed a positive linear correlation (Pnonlinear=0.844). A significant interaction between PIR and OSM was observed (Pinteraction=0.019). CONCLUSION: Serum OSM is positively and linearly associated with MASLD odds in US adults. Measuring OSM may help identify high-risk groups, enabling early intervention and informing public health strategies.