BACKGROUND: Heart rate variability (HRV) decreases in Parkinson\'s disease (PD) and it can be considered a marker for cardiovascular dysautonomia. The purpose of this pilot study is to evaluate long-term time-domain analysis of HRV of PD patients and compare the results with those of matched healthy individuals. METHODS: Idiopathic PD patients without comorbidity impairing HRV, and age-matched healthy individuals were recruited in a pilot study. A long-term time domain analysis of HRV using 24-h ambulatory ECG was performed. RESULTS: Overall, 18 PD patients fulfilling inclusion criteria completed the evaluation (mean age was 55.6 +/- 8.8, disease duration: 5.0 +/- 4.7). Mean SCOPA-AUT score was 10.1 +/- 7.3. Patients were on Hoehn & Yahr stage 1-2 and mean Levodopa Equivalent Dose (LED) was 311 +/- 239.9. Mean of the 5-min standard deviation (SD) of R-R intervals distribution (SDNN) for all 5 min segments of the entire recording (ISDNN) was significantly lower in patients compared to controls. ISDNN was significantly different between Parkinson\'s disease patients and healthy controls. CONCLUSIONS: In our population characterized by mild to moderate disease severity, time-domain assessment of HRV seemed to be a potential tool to characterize cardiovascular dysautonomia. Decrease of ISDNN in PD may reflect an autonomic derangement extending all day and night long.