Correlation of systemic immune inflammation index and systemic inflammatory response index with the severity of Parkinson’s disease

Background While the significance of inflammation in Parkinson’s disease (PD) pathogenesis has been established, the relevance of emerging hematological markers such as the systemic immune-inflammation index (SII) and systemic inflammatory response index (SIRI) to this disorder requires further investigation. Methods Whole blood were collected and analysed for the measured parameters from 222 Parkinson’s disease (PD) patients and 298 healthy controls (HCs), All PD patients undergoing comprehensive neuropsychological assessment. Partial correlation analysis was used to evaluate the correlation between SII, SIRI and PD severity, after adjusting for age. Logistic regression models were constructed to evaluate the associations of these inflammatory indices with PD risk, while receiver operating characteristic (ROC) analysis assessed their diagnostic performance. Results The SII and SIRI were substantially higher in patients with PD than in HCs. Both the SII and SIRI were positively correlated with Hoehn and Yahr staging scale (H&Y), Unified Parkinson’s Disease Rating Scale (UPDRS), UPDRS-I, UPDRS-II, and UPDRS-III scores. Conversely, the SII exhibited a negative relationship with Mini-Mental State Examination (MMSE) scores. A binary logistic regression model demonstrated that the SII [odds ratio (OR), 1.601; 95% confidence interval (CI) 1.484–1.828, p < 0.001] and SIRI (OR, 1.487; 95% CI, 1.319–1.609, p < 0.001) were independent factors for PD. The area under the curve (AUC) values for the SII, SIRI, and SII & SIRI for PD were 0.750, 0.700, and 0.785, respectively. Conclusion Our findings support the potential utility of elevated SII and SIRI as biomarkers for assessing PD severity.