Association between the systemic immune-inflammation index and metabolic syndrome and its components: results from the multi-ethnic study of atherosclerosis (MESA)

The Systemic Immune-Inflammation Index (SII) is a novel biomarker of systemic inflammation. We explored the association between the SII and metabolic syndrome (MetS) and its components in middle-aged and older adults. We included 2755 participants (1305 men) aged 45–84 years from the Multi-Ethnic Study of Atherosclerosis (MESA) cohort from examination 5 (2010–2012). Logistic regression was employed to assess the relationship between the SII and MetS, as well as its components. A total of 1082 participants (463 men) were diagnosed with MetS. On a continuous scale, the SII was positively associated with MetS (odds ratio (OR): 1.23, 95% confidence interval (CI): 1.05–1.46) and its components including hyperglycemia (1.23: 1.05–1.44) and elevated blood pressure (BP) (1.47: 1.14–1.89). When analyzed on a quartile scale, participants in the quartile 4 of SII had 32% and 63% higher prevalence of hyperglycemia and elevated BP, respectively, compared to those in the quartile 1 (P for trend: 0.021 and < 0.001, respectively). Additionally, we identified 40% higher prevalence of low HDL-C in quartile 2 of the SII compared to quartile 1 (1.40; 1.07–1.83) (P trend = 0.454). In subgroup analysis, general obesity status modified the relationship between SII and abdominal obesity, showing a positive association in obese individuals (1.72: 1.00-2.95) and a negative association (0.80: 0.66–0.97) in non-obese individuals (P for interaction = 0.009). Higher SII scores were associated with an increased likelihood of MetS, hyperglycemia, and high BP among middle-aged and older adults. Longitudinal studies are needed to determine the causal relationships between SII and the development of MetS, as well as to assess the potential role of SII as a screening tool in clinical practice.