Associations of Systemic Inflammation Response Index (SIRI) with Risk of Cardiovascular Diseases Across Age and Gender Groups: A Retrospective Analysis of NHANES 2021-2023

Background : Systemic inflammation is a contributor to the pathogenesis of cardiovascular diseases, such as congestive heart failure (CHF), coronary artery disease (CAD), and stroke. Systemic inflammation response index (SIRI), a simple measure of systemic inflammation, is calculated using absolute monocyte, neutrophil, and lymphocyte counts. Whether SIRI can be used as a screening test for cardiovascular diseases across different age and gender groups remains unclear. This retrospective analysis of the National Health and Nutrition Examination Survey (NHANES) data aimed to explore SIRI as a screening test for selected cardiovascular diseases across age and gender groups. Methods : This study analyzed the complete blood count (CBC-L) and medical conditions (MCQ-L) datasheets of NHANES 2021-2023. SIRI was calculated using CBC-L data as absolute monocytes ×absolute neutrophils ÷ absolute lymphocytes; quartiles of SIRI were calculated. Prevalences of CHF, CAD, angina, heart attack, and stroke were calculated using MCQ-L; their prevalence and burden were also calculated according to SIRI quartiles. Considering SIRI as the independent predictor, Receiver Operating Curve (ROC) analysis was performed for each disease to determine the area under the ROC curve (AUC) and clinically useful SIRI values. Results : A total of 5757 participants, who had data available for both CBC-L and MCQ-L, were analyzed. Overall, the self-reported prevalences of CHF, CAD, angina, heart attack, and stroke were 4.2%, 5.4%, 2.3%, 4.3%, and 4.5%, respectively. SIRI quartiles were as follows: Q1: SIRI <0.7; Q2: 0.7−1.04, Q3: 1.04−1.54; and Q4: >1.54. Prevalence of each disease increased significantly from Q1 to Q4 (particularly steeply for Q4); for instance, the prevalence of CAD was as follows; Q1: 2.2%; Q2: 3.6%; Q3: 5.6%; and Q4: 10.3%; p=0.000). The participants in Q4, with SIRI>1.54, also had the highest burden of each disease, ranging from 37.3% of the total burden for stroke to 47.4% for CAD. However, Q4 SIRI values were associated with old age (age>59) and males. ROC analysis showed that SIRI was a significant predictor for the prevalence of all five diseases, with the AUC values ranging from 0.598 for stroke to 0.673 for CAD. For each disease, SIRI values close to 0.6 and 2.2 were associated with 90% sensitivity and 90% specificity, respectively. Conclusion: This analysis suggests that a high SIRI, particularly that >1.54, is associated with a high prevalence and burden of cardiovascular diseases. Certain SIRI values can reach up to 90% sensitivity (SIRI=0.6) or specificity (SIRI=2.2). These estimates could help inform and augment cardiovascular disease screening interventions, especially for the subsets of older individuals and men.