Relationship between nonmotor symptoms and neutrophil-to-lymphocyte ratio in Parkinson's disease

Purpose: The aim of this study was to investigate the relationship between neutrophil-to-lymphocyte ratio (NLR), an inflammation marker, and nonmotor symptoms, such as fatigue, sleep disturbances, and overall quality of life, in Parkinson's disease (PD). Materials and Methods: This study included 60 patients diagnosed with PD (17 female and 43 male). Fatigue was assessed using the Parkinson's Disease Fatigue Scale (PFS16), sleep quality using the Parkinson's Disease Sleep Scale (PDSS), and quality of life using the Parkinson's Disease Questionnaire-8 (PDQ-8). Neutrophil and lymphocyte counts were extracted from the complete blood count results, and the NLR was calculated. Results: A moderate, negative correlation was observed between fatigue and sleep quality; a moderate, positive correlation was observed between quality of life, motor rating, and disease staging; a moderate, negative correlation was observed between sleep quality and quality of life; a weak, negative correlation was observed between sleep quality, motor rating, and disease staging; and a weak, positive correlation was found between quality of life, motor rating, and disease staging. No significant relationship was observed between NLR and nonmotor symptoms in PD. Conclusion: Further prospective studies with larger samples or case-control designs are warranted to explore the potential clinical utility of a simple, cost-effective biomarker, such as NLR, in assessing PD symptoms and disease progression.