Peripheral Inflammation Markers in Drug-induced Parkinsonism: Findings from a Community-based Cohort
Brandon Lien1, Mariel Mawad2, Mason Usher1, Anwen Lin2, Saud Alhusaini1
1Brown University, 2Warren Alpert Medical School of Brown University
Objective:
To investigate the potential role of peripheral inflammation markers in drug-induced parkinsonism (DIP).
Background:
Neutrophil-to-lymphocyte ratio (NLR) is a widely utilized biomarker reflecting peripheral inflammation. Elevated NLR has been associated with Parkinson’s disease (PD) and several other neurodegenerative disorders. Given that DIP is associated with increased risk of PD, it remains unclear if elevated NLR is also associated with DIP.
Design/Methods:

We evaluated 25,000 community-based healthy individuals (with no known inflammatory or autoimmune diseases, blood disorders, or neurologic or psychiatric conditions), 1078 idiopathic PD patients, and 108 DIP patients from the UK Biobank, a publicly available biomedical database containing health information, biological samples, imaging data, and genetic information from over half a million community-based UK participants. We only included incident PD and DIP cases (diagnosed after initial enrollment). Independent regression models were applied to examine between-group differences in neutrophil and lymphocyte counts and NLR while accounting for relevant covariates (e.g., age and sex).

Results:

Higher neutrophil count and NLR were identified in PD (p < 0.01) and DIP patients (p < 0.001). Meanwhile, a significantly lower lymphocyte count was noted in PD patients (p < 0.001). After accounting for the effect of the underlying psychiatric condition, the association between DIP and higher neutrophil count and NLR was no longer significant. Instead, the higher neutrophil count and NLR appeared specific to DIP patients with an underlying schizophrenia or bipolar disorder.

Conclusions:
DIP is associated with a higher neutrophil count and NLR. This association appeared driven by the underlying psychiatric disorder, particularly bipolar disorder and schizophrenia. These findings highlight the role of peripheral inflammation in brain-related disorders and possible shared mechanisms with idiopathic PD.
10.1212/WNL.0000000000208968
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