Correlation between non-marker inflammatory indices and carotid intima-media thickness in the middle-aged and elderly adults

Objectives This study aimed to investigate the correlations between carotid intima-media thickness (IMT) and systemic immune inflammation index (SII), platelet-to-lymphocyte ratio (PLR), and neutrophil-to-lymphocyte (NLR) ratio. Materials and methods This was a cross-sectional study enrolling a total of 582 middle-aged and elderly patients. The correlations between SII, PLR, and NLR with IMT were assessed using logistic regression models, which were subsequently incorporated into the underlying models with traditional risk factors and their predictive values for IMT. Results NLR exhibited a significant correlation with IMT in the simple regression analysis (β=0.01, 95%CI= 0.00-0.02, p<0.05). After controlling for potential confounding variables in the multivariate analysis, the association between NLR and both Maximum IMT [β=0.04, 95%CI=0.02-0.07, p=0.0006] and Mean IMT [β=0.05, 95%CI=0.02-0.07, p=0.0001] remained statistically significant. Additionally, PLR was found to be a significant independent predictor of Maximum IMT [β=0.04, 95% CI =0.00-0.07, p=0.0242] and Mean IMT [β=0.04, 95% CI=0.01-0.07, p=0.0061]. Similarly, SII was identified as an independent predictor of Maximum IMT [β=1.87, 95% CI =1.24, p=0.0003]. The study found a significant positive correlation between Maximum IMT and the levels NLR, PLR, and SII. Specifically, in the Maximum IMT group, higher quartiles of NLR, PLR, and SII were associated with increased odds ratios (OR) for elevated IMT levels, with statistically significant results for NLR (Q4vsQ1: OR 3.87, 95% CI 1.81-8.29), PLR (Q4vsQ1: OR 2.84, 95% CI 1.36-5.95), and SII (Q4vsQ1: OR 2.64, 95% CI 1.30-5.37). Finally, the inclusion of NLR, PLR, and NLR+PLR+SII in the initial model with traditional risk factors resulted in a marginal improvement in the predictive ability for Maximum IMT, as evidenced by the net reclassification index (p<0.05). Conclusions This study discovered a positive correlation between SII, PLR, NLR, and IMT, which are likely to emerge as new predictors for IMT thickening. These findings lay a theoretical reference for future predictive research and pathophysiological research on carotid intima-media thickening.