2.1. Databases

A total of 221 French speakers were included in this study: 121 PD patients and 100 healthy controls (HC). All PD patients and 49 HC were recruited at the Pitié-Salpêtrière Hospital and included in the ICEBERG cohort, a longitudinal observational study conducted at the Clinical Investigation Center for Neurosciences at the Paris Brain Institute (ICM). An additional 51 HC were recruited to balance the number of PD and control subjects. All patients had a diagnosis of PD, according to the United Kingdom Parkinson's Disease Society Brain Bank (UKPDSBB) criteria, <4 years prior to the study. HC were free of any neurological diseases or symptoms. Participants had a neurological examination, motor and cognitive tests, biological sampling, and brain MRI. PD patients were pharmacologically treated and their voices were recorded during ON-state (<12 h after their last medication intake). Data from participants with technical recording issues, language disorders not related to PD (such as stuttering) or when a deviation from the standardized procedure occurred, were excluded from the analysis. The ICEBERG cohort (clinicaltrials.gov, {"type":"clinical-trial","attrs":{"text":"NCT02305147","term_id":"NCT02305147"}}NCT02305147) was conducted according to Good Clinical Practice guidelines. All participants received informed consent prior to any investigation. The study was sponsored by Inserm, and received approval from an ethical committee (IRBParis VI, RCB: 2014-A00725-42) according to local regulations.

Among the 217 participants kept for the analysis, 206 subjects including 115 PD (74 males, 41 females) and 91 HC (48 males, 42 females) performed speech tasks recorded with a high-quality microphone. Information about age, time since diagnosis, Hoehn and Yahr stage (Hoehn and Yahr, 1967), Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) III score (Goetz et al., 2007) (OFF state) and Levodopa Equivalent Daily Dose (LEDD) are detailed in Table 2. The microphone was a professional head mounted omnidirectional condenser microphone (Beyerdynamics Opus 55 mk ii) placed approximately 10 cm from the mouth. This microphone was connected to a professional sound card (Scarlett 2i2, Focusrite) which provided phantom power and pre-amplification. Speech was sampled at 96,000 Hz with 24 bits resolution and a frequency range of 50 Hz–20 kHz. ICEBERG participants were recorded in consultation rooms in the Clinical Investigation Center of the Paris Brain Institute or in the Sleep Disorders Unit of the Pitié-Salpêtrière hospital in Paris. Additional HC were recorded in quiet rooms in their own house or at their office with the same recording devices. Speech tasks were presented in a random order to the participants via a graphical user interface. The tasks which are analyzed in the present study are: reading (1 min), sentence repetition (10 s), free speech (participants were asked to talk about their day during 1 min) and fast syllable repetitions (1.5 min), also called diadochokinesia (DDK) tasks. Details about speech task content are presented in Annex 1.

High-quality microphone database information.

Most of the participants, 101 PD (63 males, 38 females) and 61 HC (36 males, 25 females) also carried out telephone recordings. Information about age, time since diagnosis, Hoehn and Yahr stage, MDS-UPDRS III score (OFF state), and LEDD are detailed in Table 3. Participants called once a month an interactive voicemail (IVM, from NCH company), connected to a SIP (Session Initiation Protocol) server (ippi), with their own phone (mobile or landline). Audio signal was compressed with G711 codec and transformed into PCM16 audio files by IVM. Finally, speech files were sampled at 8,000 Hz with 16 bits resolution, and a frequency bandwidth of 300–3,400 Hz. We set up the voicemail to automatically make the participants carry out a set of speech tasks when they called. Participants performed different numbers of recording sessions (from 1 to 13 with an average of 5) depending on when they started and stopped. The tasks that we analyzed in this study were: sentence repetition (20 s), free speech (1 min) and DDK tasks (1 min). For practical reasons, only audio instructions were given during the phone calls. Therefore no reading tasks were performed. Details about speech task content are presented in Annex 1, and transmission chain and encoding are described in Annex 2.

Telephone database information.