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).

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.