Circadian rhythm of heart-rate variability and autonomic cardiovascular regulation in Parkinson's disease

In a study of the circadian rhythm of heart-rate variability (HRV) comparing autonomic cardiovascular regulation in normal subjects and those with Parkinson's disease (PD), we used spectral analysis and low-frequency (LF) and high-frequency (HF) components determined from Holter electrocardiography (ECG). We found HRV parameters such as LF and HF components and the LF component/HF component (LF/HF) ratio over a 24-hour period to be lower in the PD group than in the control group, indicating that PD led to cardiovascular sympathetic and parasympathetic nervous dysfunction. HRV parameters at 1-hour intervals in the PD group were invariably lower than in the control group, and the circadian rhythm of parameters was disturbed in PD, indicating that patients with PD had circadian rhythm impaired in autonomic cardiovascular regulation. The Hoehn and Yahr stage correlated significantly with LF and HF components and the LF/HF ratio. Autonomic nervous dysfunction thus progressed in parallel with motor disturbance in PD. Calculating LF and HF components and the LF/HF ratio for 24 hours using spectral analysis proved useful in observing sympathetic and parasympathetic cardiovascular regulation in PD.