Scoping review of the relationship between xerostomia and voice quality.

PURPOSE: This scoping review aims to synthesize all of the currently available information on how xerostomia correlates with vocal function and the mechanisms that underpin it. METHODS: Our scoping review used PubMed, Scopus, Embase, and Web of Science databases to review articles published between January 1999 and July 2022 in accordance with the PRISMA-ScR guidelines. In addition to the academic databases, we also conducted a manual search of Google Scholar. Further investigation was conducted on studies that examined the relationship between xerostomia and vocal function. RESULTS: Of the 682 initially identified articles, 21 met our inclusion criteria. Among the included studies, two articles (n = 2) revealed the mechanistic relationship between xerostomia and vocal function. Most studies (n = 12) focused on xerostomia secondary to other underlying conditions or treatments, among which radiotherapy and Sjögren's syndrome were commonly investigated. Seven studies (n = 7) provided details about common vocal parameters measured in studies of xerostomia and the voice. CONCLUSION: The literature currently lacks publications regarding the relationship between xerostomia and vocal function. Most of the studies included in this review were about xerostomia secondary to other conditions or medical treatments. Therefore, the impacts on the voice that were observed were very multifaceted and the role of xerostomia alone in phonation could not be ascertained. Nevertheless, it is clear that dryness in the mouth plays some role in vocal function and further research should focus on clarifying and finding the underlying mechanism behind this relationship by incorporating high-speed imaging and cepstral peak prominence analyses.