Systemic inflammation response index and Parkinson's disease risk: A cross-sectional study

Parkinson's disease (PD) is a highly prevalent neurodegenerative disorder, and inflammation plays a critical role in its pathogenesis. The systemic inflammation response index (SIRI) reflects the overall inflammatory status and has been associated with the development of various diseases. This study aims to investigate the association between the SIRI and PD. Data was obtained from the National Health and Nutrition Examination Survey from 2003 to 2020. A total of 29,022 participants aged ≥40 years were included, of whom 275 were diagnosed with PD. Weighted multivariable logistic regression models were used to evaluate the association between the SIRI and PD, with progressive adjustments for demographic and clinical covariates. Restricted cubic spline regression was used to assess potential nonlinearity, whereas subgroup analyses were used to examine effect modifications. The predictive performance of the SIRI for PD was evaluated via receiver operating characteristic curves. PD patients were older and had higher prevalence of hypertension, diabetes, body mass index, and SIRI level compared with non-PD participants (all P < .05). In unadjusted analysis, each unit increase in SIRI was associated with higher odds of PD (odds ratio = 1.208, 95% confidence interval: 1.112-1.313, P < .001). The association remained significant after full adjustment (odds ratio = 1.162, 95% confidence interval: 1.051-1.285, P = .004). Restricted cubic spline analysis revealed a positive association between the SIRI and PD prevalence (P-overall < .001), with evidence of a nonlinear trend (P-nonlinear = .047). Subgroup analyses showed consistent results across age, sex, race, education level, body mass index, hypertension, diabetes, and smoke, with no significant interactions. The predictive ability of the SIRI for PD was modest, with an area under the receiver operating characteristic curve (area under the curve) of 0.579. Our findings demonstrate a significant dose-response association between the SIRI and PD. This highlights the potential utility of the SIRI as a predictive biomarker, which may be incorporated into screening frameworks to facilitate early detection and preventive interventions.