Original data.

Background
Sarcopenia is closely linked to inflammation; however, the association between the systemic inflammatory response index (SIRI) and mortality in patients with sarcopenia remains unclear. This study aims to explore the relationship between SIRI and mortality in sarcopenia patients.
Methods
We analyzed data from ten cycles of the National Health and Nutrition Examination Survey (NHANES) spanning 1999 to 2018, selecting 3,141 sarcopenia patients. Mortality data were obtained from the National Death Index up to December 31, 2019. Participants were divided into three groups based on the ranking of their SIRI values. The association between SIRI and mortality was assessed using Cox proportional hazards models, with smooth curve fitting employed to test the correlation. Sensitivity analyses, subgroup analyses, and interaction tests were conducted to validate the stability of the findings.
Results
A total of 101,316 individuals were included in this study. During a median follow-up of 10.4 years (minimum follow-up time of approximately 0.08 years, maximum follow-up time of 20.75 years), 667 participants died. Kaplan-Meier (KM) analysis indicated a higher risk of mortality in the SIRI Q3 group. Cox regression analysis showed a significant association between the SIRI Q3 group and all-cause mortality [HR 1.24 (95% CI: 1.05, 1.47)] and cardiovascular disease mortality [HR 1.46 (95% CI: 1.04, 2.04)]. Subgroup analysis revealed that SIRI was significantly associated with all-cause mortality across various demographic characteristics (e.g., gender, diabetes, hypertension, cardiovascular disease). Sensitivity analysis, excluding participants with cardiovascular disease, those who died within two years of follow-up, and those under 50 years old, indicated higher hazard ratios (HRs) for all-cause and cardiovascular mortality in the SIRI Q3 group.
Conclusion
This study demonstrates a significant association between SIRI and an increased risk of mortality in sarcopenia patients aged 20 years and older.