Heart Rate Variability and Cognitive Impairment in Parkinson’s Disease

Abstract

Objective: To evaluate the association between the heart rate variability (HRV) and cognitive impairment in PD patients.Background: Emerging evidence suggests an association between cognitive impairment and autonomic dysfunction in Parkinson?s disease (PD). However, there is lack of information between the relationship of HRV and changes in cognition in this population.Method: Nineteen consecutive PD patients without dementia in Hoehn & Yahr stage 2.1±0.2 mean (SD) enrolled in a prospective study of Fear of Falling and falls were assessed by short-term HRV analysis and blood pressure measures during postural changes. EKG were recorded during 5 minutes in resting (RS) and standing (SS) states. Time domain (Mean RR, SDNN, RMSSD), frequency domain (VLF, LF, HF, LF/HF) and non-linear (DFA α1, DFA α2, SampEn) parameters were calculated. Data in RS and SS and its difference (DS) were analyzed. Cognitive performance was evaluated by MoCA, Frontal Assessment battery [FAB], Trail making test [TMT-B], Digit symbol modality test [DSMT], phonemic fluency and Stroop word-color test [SCWT].Results: Eleven patients (57%) were classified as mild cognitive impairment (PD-MCI) by MoCA. The mean (SD) of age and illness duration were 70.9 ± 6.5 and 8.1 ± 4.7 years respectively. There was no difference in age, gender, illness duration, blood pressure, LED or any MDS-UPDRS scores between groups with or without MCI; MCI-group showed significantly higher LF/HF-SS ratio (p=0.032), lower RMSSD-DS (p=0.003) and lower SampEn-DS (p=0.032) than non-MCI group. The poorer performance in multiple cognitive domain tests was significantly associated with HRV indexes: the phonemic fluency scores with reduced overall HRV (RMSSD-SS p=0.016; SDNN-RS p=0.039; SDNN-SS p=0.016); decreased baroreflex function (LF-SS p=0.029; HF-RS p=0.017; HF-SS p=0.037) and SampEn-SS p=0.049); MoCA test was associated to lower RMSSD-DS (p=0.003) and higher DFA α2-SS (p=0.044); SWCT was associated to higher values of DFA α2-SS (p=0.026) and DFA α2-DS (p=0.024). No significant differences were found between groups with or without MCI or any independent cognitive test and blood pressure measures during postural changes.Conclusion: Reduced HRV reflecting decreased parasympathetic activity independently of orthostatic hypotension is significantly associated with PD-MCI. Considering the high rate of conversion of PD-MCI to PDD its role as predictive biomarker should be explored in future studies.