Association of Cardiac Autonomic Dysfunction and Cognitive Impairment With Disease Severity in Parkinson’s Disease: A Cross-Sectional Study

Background Parkinson's disease (PD) is a neurodegenerative disorder characterized by the presence of both motor and non-motor features. Although cardiac autonomic imbalance and cognitive derangement are well documented in PD, their relationship with the severity of the disease has not been explored using a multimodal approach. Objective This study aimed to assess the correlation between cardiac autonomic function, cognitive parameters (P300 and reaction time), and biochemical markers (homocysteine (HCY) and 8-hydroxy-2′-deoxyguanosine (8-OHdG)) with disease severity in individuals with mild-to-moderate PD. Methods Forty individuals aged 35 to 70 years diagnosed with PD were recruited. Cardiac autonomic function was assessed using heart rate variability (HRV) analysis and conventional autonomic function tests. Cognitive function was evaluated by recording P300 event-related potentials and auditory and visual reaction time. Serum HCY and serum 8‑OHdG were measured as biomarkers of cardiovascular risk and oxidative stress, respectively, using ELISA. Disease severity was assessed using the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III. Correlation between the study parameters was assessed using the Pearson or Spearman’s rank correlation coefficient test. P<0.05 was considered statistically significant. Results Significant positive correlations were observed between UPDRS scores and HRV indices of sympathetic activity (LF power, LFnu), sympathovagal balance (LF/HF), P300 latency, reaction times, and biomarker levels. Significant negative correlations were observed between UPDRS scores and parasympathetic HRV indices (HF power, HF nu), total HRV, conventional autonomic function parameters, and P300 amplitude. Conclusion Increasing disease severity in PD is associated with cardiac autonomic imbalance, cognitive impairment, and elevated markers of cardiovascular risk and oxidative stress, suggesting a multi-system involvement.