Voice fundamental characteristics in Parkinson's disease: a case-control study of the Moroccan population

Parkinson's Disease (PD) is the second most common neurodegenerative disorder. Hypokinetic dysarthria, a motor speech disorder affects approximately 90% of PD patients. In Morocco, linguistic features of Moroccan Arabic may influence how voice impairment appear in PD. This study investigates the acoustic characteristics of Moroccan PD patients' voices. This was a case-control study involving 30 Moroccan PD patients, both medicated and unmedicated) and 30 healthy control participants. Voice recordings were collected from participants before and after dopaminergic treatment. Four tasks were performed: sustained vowel production, spontaneous speech, diadochokinesis, and reading tasks in both Arabic and French. The Unified Parkinson's Disease Rating Scale was computed for each state and data were analyzed using PRAAT software (v6.2), for phonatory and articulatory parameters. PD patients exhibited significant alterations in shimmer, jitter, and Harmonics-to-Noise and Noise-to-Harmonic Ratios, reflecting pitch and vocal intensity instability. A "hoarse" and "breathy" vocal quality was noted. Rhythm disturbances were marked by an increased number of long pauses (≥500 ms), indicating difficulty in sustaining speech flow. No adverse events were reported. Moroccan PD patients exhibit distinctive voice and rhythm abnormalities, particularly in vowel articulation, phonation, and timing. These markers may serve as reliable indicators for PD diagnosis and progression.