Persistent Gustatory Dysfunction in COVID-19 Survivors: A Narrative Literature Review
Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibit a diverse spectrum of clinical manifestations, some of which last for a long time, making a great impact on the healthcare of patients who recovered from coronavirus disease 2019 (COVID-19). Although taste disorders have been well-recognized to be closely associated with COVID-19, understanding of gustatory sequelae is relatively poor compared with oral symptoms in the early phase of COVID-19. The aim of this study was to characterize gustatory dysfunction in COVID-19 survivors by a narrative literature review of follow-up studies and to speculate the pathogenic mechanisms underlying such a persistent symptom. Scientific articles were retrieved by searching PubMed, LitCovid, ProQuest, medRxiv and bioRxiv from 1 April 2020 with a cut-off date of 10 September 2021. The follow-up time periods of the relevant 49 studies ranged from 4 weeks to 12 months. Results of the literature search indicated that ageusia, hypogeusia and/or dysgeusia persist in up to 45.0% of COVID-19 survivors and that the prevalence of these taste impairments varies depending on ethnicity, age, gender and disease severity of patients. Gustatory dysfunction can be detected at high frequency even one year after symptom onset. Persistence of gustatory dysfunction is pathogenically related to expression of SARS-CoV-2 cellular entry-relevant receptors in taste cells and neural cells, decreased saliva secretion, zinc deficiency, disturbed nervous system and inflammation associated with persistent SARS-CoV-2 infection. Given the long-term persistence of gustatory dysfunction in COVID-19 survivors, their discharge from hospital is not the end of disease. Careful attention should be continuously paid to taste perception of post-COVID-19 patients to recover the health-relating quality of life, which is required for health providers, especially dental professionals who not only may experience COVID-19 survivors but also can easily become aware of their taste abnormalities.