What are the Symptoms that Characterize the Clinical Condition of Vocal Fatigue? A Scoping Review and Meta-Analysis

Introduction: Vocal fatigue is a clinical manifestation associated with a perception of negative vocal adjustment. It is related to the increase in the sensation of excessive effort when speaking and the lack of conditioning of the muscles and structures that involve vocal production. Because it has a complex and multifactorial diagnosis, there is still no consensus on the symptoms most commonly found in this clinical condition.

Objective: To review and analyze the symptoms that characterize the clinical condition of vocal fatigue.

Methods: This study consists of a scoping review carried out in the Cochrane Library, Embase, Lilacs, and Medline databases. Observational studies or clinical trials from the last 10 years. Studies with participants younger than 18 years of age were excluded; as well as research that did not describe symptoms of vocal fatigue or that presented vocal fatigue as a symptom; studies with patients with neurological, psychiatric, syndromic conditions, or head and neck cancer. The Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies NHLBI-NIH scale was used to assess the methodological quality of selected observational studies and the PEDro scale for the analysis of experimental studies. The steps were performed by three blinded evaluators. Subsequently, meta-analyses of global means were executed for each factor under study; a comparison of the difference in the mean score for each factor between exposed and unexposed; a comparison of the difference in the average score, among non-professional voice users, for each factor between exposed and unexposed.

Results: In the searches performed, 956 articles were found and 29 articles were selected according to the eligibility criteria. Of these, 93.11% of the studies were observational and 6.89% were clinical trials. Regarding the gender and age group of the study samples, women aged between 30 and 45 years were predominant. As for the occupational use of voice, 68.97% of the samples were composed of professional voice users and 31.03% of non-professional voice users, with most professional voice users being teachers and non-professional voice users, individuals with dysphonia or vocal complaint. To assess vocal fatigue symptoms, 28 studies used the Vocal Fatigue Index (VFI) protocol, and only one study used another assessment protocol, Self-Administered Voice Rating. All studies were classified as regular, according to the scale used. As for the meta-analyses performed, the mean scores of the VFI factors were higher among professional voice users when compared to non-professional voice users and higher in dysphonic individuals compared to non-dysphonic individuals.

Conclusion: The vocal fatigue symptoms found in this review were common in the populations of professional voice users and non-professional voice users and dysphonic and non-dysphonic individuals. These symptoms were related to vocal recovery after rest, physical discomfort, and restricted vocal use.