Unravelling Health and Frequent Symptoms and Voice Characteristics Evolution Over Time of Users of the Long COVID Companion Application to Develop Voice Biomarkers of Frequent Long Covid-related Symptoms

Five years after the start of the COVID-19 pandemic, it has been estimated that a mean of 10-20% of COVID-19 patients will develop Long COVID, which represents at least 65 million people worldwide. In Luxembourg, based on the current status of the COVID-19 pandemic and the prevalence of Long COVID in other countries, we estimate that approximately 25,000 individuals may have been affected by Long COVID.

People with Long COVID (PWLC) present complaints such as tachycardia, extreme fatigue, dyspnea, and inability to perform daily physical tasks. More than 200 symptoms have been associated with Long COVID, and multiple organs are affected. Our previous work showed that 59% of COVID-19-infected people from the PrediCOVID cohort study reported 1 or more persisting symptom(s) after one year. The number of persisting symptoms increased with the initial disease severity, and the quality of life of those participants was notably impacted by sleep disorders (54%) and compromised respiratory function (12.9%). Nonetheless, individuals with an initially asymptomatic or mild form of COVID-19 infection could also be affected.

Long COVID care, as for other chronic diseases, should align with the concept of minimally disruptive medicine, aiming for a reduced burden on patients' lives while maximizing health outcomes. PWLC frequently have several healthcare professionals in charge of different aspects of their care, with many appointments and travels to manage. They are also regularly asked to complete long standardized questionnaires or scales to evaluate their symptoms, which generates an avoidable burden on their lives if care is not coordinated. The development of innovative methods to integrate multiple Patient Report Outcomes in a portable, versatile way, to reduce travels for medical care, and overall for remote health's monitoring is therefore of the highest importance.

Few existing apps that could meet the needs of PWLC already exist, such as "Visible" or "Living With". However, these apps are only available in the US and in the UK, respectively. Furthermore, the "Living with" app is available only by invitation. This limits their availability for PWLC in Europe. Some other apps designed for other chronic conditions, like myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) Pacing app, are also used by some PWLC to manage their daily energy levels. However, these apps do not fully meet the specific needs of PWLC, and are only available in specific countries, in English, and some of them only on the iOS operating system, which restricts their potential use.

Voice is a promising candidate increasingly used in mobile health (mHealth) interactions in chronic diseases. Voice is an easy and cheap medium to collect and can be easily integrated into a device like a smartphone, now widely used by people of different ages and education levels. It can be used for vocal biomarker assessment as new clinical endpoints for relevant symptoms. Vocal biomarker candidates have already been identified by the Deep Digital Phenotyping (DDP) research team, based on data from the PrediCOVID cohort study, with performances above 80% to detect fatigue, loss of taste and smell, and symptomatic status in COVID-19-infected people. However, further progress is required before these vocal biomarkers can be used in clinical practice. New vocal biomarkers of global health status or of other symptoms need to be developed to allow a more personalized monitoring of PWLC.