Prognostic significance of peripheral lymphocyte counts in Parkinson's disease.

Background: Inflammation plays a pivotal role in the pathogenesis of Parkinson's disease (PD). The aim of this study was to explore whether peripheral blood markers are associated with subsequent disease outcomes in patients with PD. Methods: We conducted a follow-up study among consecutive patients with PD and investigated the association between outcomes and baseline blood markers, including neutrophil, lymphocyte, and monocyte counts; the neutrophil-to-lymphocyte ratio; motor/nonmotor symptoms; and radionuclide scanning findings. Results: Of the 112 patients, 97 (87%) met the eligible criteria. Over the average 1800-day follow-up period, 33 patients completed the full follow-up, 30 patients reached an endpoint (death, 3; hospitalization, 12; and placement in a nursing home, 6; home medical care 9), and 34 patients were censored. At the baseline assessment, patients who reached an endpoint were older and had higher Hoehn and Yahr stages and motor symptom scores, larger reductions in cardiac metaiodobenzylguanidine scintigraphy accumulation and lower peripheral lymphocyte counts than patients who completed follow-up or were censored. Kaplan-Meier curve analysis revealed that patients who had low peripheral lymphocyte counts had a shorter time to reach an endpoint than those with preserved lymphocyte counts. According to the multivariate Cox proportional hazards regression analysis, motor symptoms and peripheral lymphocyte count were associated with reaching an endpoint. Conclusions: Among the blood biomarkers, a lower lymphocyte count was associated with worse outcomes in patients with PD. Low peripheral lymphocyte counts may be predictive of subsequent worse PD outcomes.