Systemic inflammatory response index is associated with increased all-cause and cardiovascular mortality in obstructive sleep apnea: evidence from NHANES and validation with an external hospital-based dataset

Objective Obstructive sleep apnea (OSA) is increasingly recognized for its association with significant morbidity and mortality. Despite advances in understanding OSA’s impacts, the role of systemic inflammation in this context remains underexplored. The systemic inflammatory response index (SIRI) has emerged as a potential marker for evaluating inflammatory status and predicting adverse health outcomes. We aim to examine the association between the SIRI and the risks of all-cause and cardiovascular mortality in individuals exhibiting symptoms of obstructive sleep apnea (OSA), with further validation in patients with diagnosed OSA. Methods A cohort of 9,992 adults with OSA symptoms was derived from the National Health and Nutrition Examination Survey (NHANES) for model development, and an independent external validation cohort of 994 patients with OSA was obtained from the Central Hospital of Wuhan. Multivariate weighted Cox regression, subgroup analyses, restricted cubic spline (RCS) analyses, and receiver operating characteristic (ROC) curves were employed to assess mortality risk in the exploratory cohort, with external validation performed using the Wuhan cohort. Results In the NHANES dataset, elevated SIRI levels were identified as significant independent risk factors for all-cause mortality (adjusted HR = 1.51, 95% CI: 1.16–1.97, p < 0.001) and cardiovascular mortality (adjusted HR = 2.03, 95% CI: 1.17–3.54, p < 0.001) among individuals with OSA symptoms. RCS analysis revealed a non-linear relationship between SIRI and both all-cause and cardiovascular mortality (both p for non-linearity <0.001). Moreover, SIRI demonstrated substantial predictive value for all-cause mortality (AUC = 0.822) and cardiovascular mortality (AUC = 0.806) in this population. These findings were further confirmed in the external validation cohort from the Central Hospital of Wuhan. In this independent dataset, RCS analysis consistently demonstrated a non-linear positive association between SIRI and mortality outcomes, and ROC analysis yielded AUC values of 0.780 for all-cause mortality and 0.866 for cardiovascular mortality, respectively. Conclusion SIRI serves as a significant predictor of mortality in individuals with OSA, highlighting its potential utility in early risk screening for long-term adverse outcomes, both at the population level and clinical settings.