Parkinson's Disease dysarthria affects the speech motor control, causing alterations at the suprasegmental level of speech. In previous researches, vowel percentage (%V) and the mean interval between two consecutive vowel onset points (VtoV) were effectively used in the synchronic description of the rhythmic variations of Italian PD speech, compared to healthy speech, even at a very early stage of the disease. This study aims at verifying the early alteration of PD speech rhythm using a diachronic approach. To reach this goal, a corpus of read speech produced by a single PD subject (female, 66 years old) has been collected, consisting of 15 radiophonic speech samples (about 100 s each) on the same topic, recorded between 2001 and 2021. The speech samples were manually segmented in consonantal and vocalic intervals by means of Praat, allowing the calculation of %V and VtoV. The results show an alteration of %V values since 2018, two years before the diagnosis and the insurgence of motor symptoms. Moreover, first results of the application of the automatic segmentation performed by SPPAS on a selection of PD speech samples will also be presented.