Nonlinear Climate–Liver Gradients: Non-optimal Temperature and Variability Increase Risk of Metabolic Dysfunction-Associated Steatotic Liver Disease

Ambient temperature and temperature variability (TV) may influence metabolic dysfunction-associated steatotic liver disease (MASLD), but large-scale evidence is lacking. We aimed to quantify nonlinear associations between long-term temperature/TV exposure and MASLD prevalence in China and evaluate their global relevance. In this cross-sectional study of 33,236 adults from 33 Chinese provinces (2010–2020), MASLD was diagnosed via ultrasonography. Meteorological data were linked to residential addresses to calculate long-term temperature/TV. Generalized additive models were employed to delineate nonlinear exposure–response relationships. Global patterns were assessed using Global Burden of Disease (GBD) data in 2021 from 204 countries or territories. A reverse J-shaped relationship emerged between ambient temperature and MASLD prevalence (minimum risk at 21.4°C), with extreme cold (1st percentile) increasing risk (OR: 1.42, 95% CI: 1.11–1.82). TV exhibited a U-shaped association (threshold: 12.2°C), where extreme low (1st percentile: OR=1.38, 1.09–1.73) and high TV (99th percentile: OR=1.15, 1.02–1.34) elevated MASLD risk. Vulnerable subgroups included males, individuals ≥45 years, smokers, and obese individuals. Globally, non-optimal temperature exposure correlated strongly with age-standardized MASLD prevalence (R=0.43, p <0.001), driven predominantly by high-temperature contributions (R=0.55 vs. 0.18 for low temperature). Chronic cold exposure and extreme temperature variability independently increase MASLD risk, with amplified effects in metabolically vulnerable populations. The global correlation between non-optimal temperature exposure and MASLD burden highlights climate change as a critical modifier of liver health. Integrating temperature mitigation into public health strategies may reduce MASLD incidence amid escalating climate challenges. • First identification of nonlinear climate-liver gradients: reverse J-shaped and U-shaped relationships for ambient temperature and variability (TV) with MASLD risk. • Extreme cold and non-optimal TV independently increased MASLD risk, establishing climate instability as a metabolic hazard. • Vulnerable groups (males, ≥45 years, smokers, obese) exhibited amplified risks, demanding climate-adaptive interventions. • Global analysis linked high-temperature exposure to MASLD burden (R=0.55), signaling climate change as a planetary health threat.