Heart rate variability to differentiate essential tremor from early-stage tremor-dominant Parkinson's disease

• Differentiating between tremor-dominant PD and ET is often difficult.
• Tremor-dominant PD showed significant and severe reductions in time and frequency domain parameters of HRV compared with ET.
• HRV may be helpful to differentiate tremor-dominant PD from ET at the early stage of disease.

BackgroundEssential tremor (ET) and Parkinson's disease (PD) are the most common movement disorders in the elderly, but it is difficult to differentiate ET from early-stage tremor-dominant Parkinson's disease (TDPD).MethodsWe investigated heart rate variability (HRV) in 23 patients with ET, 27 patients with TDPD, and 23 healthy controls. HRV was determined using the RR intervals of a 5-min electrocardiogram recording. Measurements of beat-to-beat RR variability, including time domains [(standard deviation of the normal-to-normal RR interval (SDNN), and the root mean square difference of successive RR intervals (RMSSD)] and frequency domains [low-frequency (LF) and high-frequency (HF) components and total spectral power (TP)], were assessed retrospectively.xResultsIn the TDPD group, SDNN, LF, HF, and TP were significantly lower than those in the ET group. In a receiver operating characteristic area under the curve (AUC) analysis, LF was the best potential diagnostic marker (AUC = 0.87).ConclusionNon-invasive and routine electrocardiography may be helpful in differentiating ET from TDPD during the early disease stage.