Objective: To explore whether peripheral blood neutrophils and lymphocytes are associated with longitudinal motor and cognitive decline in patients with early Parkinson’s disease (PD) and, to uncover the disease-specific mechanisms underlying these associations.

Background: The peripheral blood neutrophil and lymphocyte counts and the ratio between the two indexes, which is known as the neutrophil-to-lymphocyte ratio (NLR), are easily available biomarkers that reflect the degree of peripheral inflammation.

Method: Data were obtained from the Parkinson’s Progression Markers Initiative cohort. We included 376 patients with recently diagnosed, drug-naïve PD and 178 matched healthy controls. The patients underwent annual assessments, which included the Movement Disorder Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) part 3 test to measure motor function and the Montreal Cognitive Assessment (MoCA) to measure cognitive function, for up to 8 years of follow-up. Dopamine transporter (DAT) imaging was performed at baseline and at the 1-, 2-, and 4-year follow-up visits.

Results: At baseline, patients with PD showed higher neutrophil counts and lower lymphocyte counts, resulting in a higher NLR than that in healthy controls. Higher neutrophil counts were associated with a greater increase in MDS-UPDRS part 3 scores in patients with PD (estimate: 0.25, 95% confidence interval [CI]: 0.12 to 0.37, p<0.001). Correspondingly, higher neutrophil levels were related to a greater reduction in DAT activity in the caudate (estimate: −0.007, 95% CI: −0.014 to −0.001, p=0.046) and putamen (estimate: −0.0039, 95% CI: −0.0077 to −0.0002, p=0.042). However, there were no significant effects of lymphocyte count and NLR on changes in MDS-UPDRS part 3 and MoCA scores and striatal DAT uptake over time.

Conclusion: Among the blood biomarkers, only a higher neutrophil count was associated with faster motor progression along with accelerated nigrostriatal dopaminergic degeneration in patients with PD. The impact of neutrophils and lymphocytes on longitudinal cognitive changes remains unclear.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/prognostic-significance-of-peripheral-neutrophils-and-lymphocytes-in-early-parkinsons-disease/