Knee extensor dynapenia predicts mortality risk in older adults with metabolic dysfunction-associated steatotic liver disease: A retrospective analysis based on the US National Health and Nutrition Examination Survey

Reduced muscle strength, also known as dynapenia, is common in metabolic dysfunction-associated steatotic liver disease (MASLD), but its prognostic value remains unclear. This study aimed to examine the associations between dynapenia, defined by knee extensor strength, and mortality in United States adults with MASLD. Data were drawn from 1019 adults (mean age 61.75 years; 52.23% men) aged ≥ 50 years from the 1999–2002 National Health and Nutrition Examination Survey. Dynapenia was assessed by measuring quadriceps isokinetic strength. Participants were followed-up for all-cause and cardiovascular disease (CVD) mortality. Cox proportional hazard regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). During a median follow-up of 212 months, 446 participants died, including 154 from CVD. Compared to non-dynapenic participants, those with dynapenia had increased all-cause (HR = 2.73, 95% CI: 2.24–3.34) and CVD mortality (HR = 2.63, 95% CI: 1.65–4.18). Population-attributable fraction analysis estimated that 23.4% of all-cause deaths and 29.7% of CVD deaths were theoretically attributable to dynapenia. Stratified analysis showed that the associations between dynapenia and all-cause ( P for interaction < .001) and CVD mortality ( P for interaction = .01) were stronger in non-diabetic participants. The receiver-operating characteristic curve showed that adding dynapenia significantly improved predictive discrimination and offered significant net reclassification improvement. Knee extensor dynapenia is an independent predictor of all-cause and CVD mortality in US adults with MASLD, especially those without comorbid diabetes. Thus, routine assessment of knee extensor strength may guide risk stratification and inform clinical management in patients with MASLD.