Objective: To replicate previous findings in a diverse East London population, further characterising changes in FBC constituents and evaluating their temporal association with PD diagnosis.

Background: Previous studies have demonstrated a significant decline in lymphocyte count [1] and lymphocyte-to-neutrophil (L/N) ratio [2, 3, 4] in people with Parkinson’s disease (PwP). Parkinson’s disease (PD) diagnosis is currently predicated on the presence of characteristic motor features, by which time there is an irreversible loss of dopaminergic neurons. Full blood count (FBC) data monitoring in those at higher-risk or with suspected PD may enable earlier detection and intervention.

Method: Participants were recruited from the East London Parkinson’s Disease (ELPD) project and their FBC data were obtained from NHS patient records in October 2023. Three generalised linear regression models on RStudio were used to cross-sectionally compare lymphocyte, monocyte, eosinophil, and neutrophil counts between PD patients and controls at three time points: T1) pre-diagnosis, T2) at diagnosis, T3) post-diagnosis. Whereby diagnosis preceded the first recorded FBC, only two time points were measured (T1 and T3).

Results: We included 145 (85 male and 60 female) PwP and 73 (47 male and 26 female) controls with a mean age of 70.8 (SD 10.5) and 66.1 (SD 13.0) respectively. The lymphocyte count in PD patients was significantly reduced post-diagnosis (T3), and this was observed in both unadjusted (OR: 0.88, 95% CI: 0.80-0.97, p=0.012) and fully adjusted (OR: 0.89, 95% CI: 0.79-0.99, p=0.049) models. The L/N ratio was also significantly reduced at T3 and not at any other time point. This was seen across both unadjusted (OR: 0.72, 95% CI: 0.55-0.94, p=0.017) and fully adjusted (OR: 0.74, 95% CI: 0.56-0.98 p=0.036) models. Finally, when including participants with only two time points (T1 and T3), eosinophil count was significantly reduced in PwP at T1 in an unadjusted model (OR: 0.68, 95% CI: 0.48-0.97, p=0.034).

Conclusion: These findings demonstrate a significant decline in lymphocyte count and L/N ratio among PwP following diagnosis. Although interesting, the finding of reduced eosinophils prior to diagnosis was not replicated when adjusting for covariates. Further work is needed to understand if these changes are due to the disease itself, medication effects, or if they play a causal role in the progression of PD.

References: 1. Jensen, M.P. et al. (2021) ‘Lower Lymphocyte Count is Associated With Increased Risk of Parkinson’s Disease,’ Annals of Neurology, 89(4), pp. 803–812. https://doi.org/10.1002/ana.26034.
2. Muñoz‐Delgado, L. et al. (2023) ‘Peripheral inflammatory immune response differs among sporadic and familial Parkinson’s disease,’ Npj Parkinson’s Disease, 9(1). https://doi.org/10.1038/s41531-023-00457-5.
3. Hosseini, S. et al. (2023) ‘Neutrophil to lymphocyte ratio in parkinson’s disease: a systematic review and meta-analysis,’ BMC Neurology, 23(1). https://doi.org/10.1186/s12883-023-03380-7.
4. Muñoz‐Delgado, L. et al. (2021) ‘Peripheral immune profile and Neutrophil‐to‐Lymphocyte ratio in Parkinson’s disease,’ Movement Disorders, 36(10), pp. 2426–2430. https://doi.org/10.1002/mds.28685.

« Back to 2024 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/declining-lymphocyte-count-and-lymphocyte-to-neutrophil-ratio-following-parkinsons-disease-diagnosis/