Peripheral Immune Profile and Neutrophil-to-Lymphocyte Ratio in Parkinson's Disease.

BACKGROUND The neutrophil-to-lymphocyte ratio (NLR) in peripheral blood is a well-established inflammatory marker, but its role in Parkinson's disease (PD) remains unclear. OBJECTIVES To determine whether a different peripheral immune profile and NLR were present in PD patients. METHODS We conducted a case-control study that included 377 PD patients and 355 healthy controls (HCs). Leukocytes, subpopulations, and the NLR were measured. Multivariate linear regression analyses were applied to determine the differences between groups and the association between NLR and clinical characteristics in PD. A meta-analysis was performed to clarify the association between NLR and PD. RESULTS In our case-control study, the NLR was significantly higher in PD patients compared with HCs (2.47 ± 1.1 vs. 1.98 ± 0.91, P < 0.001). No association between NLR and age at onset, disease severity, or disease duration was found. The meta-analysis showed that the NLR was likely to be higher in PD patients. CONCLUSIONS PD patients had an altered peripheral immune profile and a higher NLR compared with HCs. © 2021 International Parkinson and Movement Disorder Society.