Dysgeusia: A review in the context of COVID-19

Unveiling the Oral Lesions, Dysgeusia and Osteonecrosis Related to COVID-19: A Comprehensive Systematic Review

Background/Objectives: The oral cavity has garnered increasing attention as a site for viral infection and related pathological manifestations in coronavirus disease-19. This article aims to provide a comprehensive overview of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2)-related oral manifestations, including taste disturbances, oral lesions and osteonecrosis. Methods: A search was conducted up to September 2024 according to PRISMA (Preferred Reporting Items for Systematic Reviews) guidelines using the databases PubMed and Scopus. All the observational, case-series, case-report and cross-sectional studies written in English on oral manifestations related to COVID-19 disease and long-COVID disease were included. All other types of studies and studies based on oral manifestation after COVID-19 vaccination and oral impairment due to lockdown were excluded. The risk of bias of included studies was assessed using the Joanna Briggs Appraisal checklist. Results: A total of 104 articles including 23 case-report, 15 case-series, 8 case-control, 18 cohort and 40 cross-sectional studies were selected. The results showed that patients with COVID-19 were found to have a significantly higher prevalence of xerostomia (45-74%) and dysgeusia (32-59%) compared to non-infected individuals. Regarding oral mucosal lesions, ulcers, candidiasis and herpes simplex infections were frequently observed. As for osteonecrosis, a significant number of patients with COVID-19-associated rhinomaxillary mucormycosis presented with maxillary osteonecrosis due to fungal infection, primarily mucormycosis. The methodological quality of most of the studies was moderate/high. Conclusions: COVID-19 has been associated with a range of oral manifestations. The complex interplay of viral infection, immune response, medication use and stress likely contributes to these oral complications. Early recognition and management of these oral manifestations are crucial for improving patient outcomes and developing targeted preventive and therapeutic strategies for COVID-19-related oral health issues.

Sleep disorders as independent predictors of taste dysfunction risk

OBJECTIVES

This study aimed to investigate the association between sleep disorders and the prevalence of taste dysfunction and the mediation effect of oral microbe in adults over 40 years.

MATERIALS AND METHODS

Cross-sectional data were utilized from the National Health and Nutrition Examination Survey (2011-2014). Regression models were employed, adjusting for demographic variables and covariates. Subgroup analyses were conducted based on age, sex, ethnicity, and education level. Multiplicative interactions were assessed through likelihood ratio tests. Additionally, the impact of sleep disturbance on the alpha diversity of the oral microbiome was examined using the rank-sum test (significance threshold: p < 0.05). Mediation analysis based on oral microbiota was conducted.

RESULTS

The analysis included 4869 participants. After adjusting for adjusting for demographic variables and covariates, individuals with sleep disorders exhibited a 36% increased risk of taste dysfunctions compared to those without sleep disorders (OR: 1.36, 95% CI: 1.00-1.84, p = 0.05). Interaction analyses indicated no significant differences between sleep disorders and taste dysfunctions concerning sex, educational level, and age across various models (Crude Model, Model 1, Model 2, and Model 3; p for interaction > 0.05). Furthermore, compared with the non-sleep disorder group, patients with sleep disorders demonstrated decreased numbers of OTUs, Shannon-Wiener indices, and Faith's phylogenetic diversity indices in the oral microbiota (p < 0.05). However, the mediation analysis failed to reveal an indirect effect of oral microbiome on taste dysfunction (p > 0.05.) CONCLUSION: Sleep disorders independently correlate with a higher risk of taste dysfunctions, potentially associated with alterations in oral flora.

Pharmacological strategies and nutritional supplements for managing dysgeusia among chemotherapy patients: A systematic review

BACKGROUND/OBJECTIVE

Among the side effects of chemotherapy, there is dysgeusia, which is an alteration or damage to the taste perception that negatively impacts the biopsychosocial sphere of the patient. Therefore, it is important to recognize and manage it appropriately. The objective of this study is to identify clinical pharmacological strategies to reduce dysgeusia in chemotherapy patients.

METHODS

A systematic literature review was conducted following the PRISMA guidelines between February and May 2023, utilizing PubMed, Embase, Cochrane Library, CINAHL, and the British Nursing Database. Methodological quality and bias risk assessment were performed using the JBI framework, while evidence certainty was evaluated using the Oxford OCEBM methodology.

RESULTS

Out of 1225 consulted records, 12 articles were included. The results underscore the efficacy of diverse pharmacological interventions in mitigating dysgeusia among chemotherapy patients. These include zinc supplementation with a daily dosage ranging between 50 and 220 mg (p ≤ 0.005), lactoferrin at 250 mg thrice daily (p < 0.001), delta-9-tetrahydrocannabinol at 2 mg per day (p < 0.05), and cannabidiol at 150 mg per day (p = 0.04). All studies analysed showed a low risk of bias. The zinc and Delta-9-Tetrahydrocannabinoid treatment proved particularly promising, compared to the other treatments considered, where sample sizes were smaller and the placebo effect was not always clear.

CONCLUSION

Among the various pharmacological strategies identified, those that appear most promising concern the integration of zinc and Delta-9-Tetrahydrocannabinoid. Future studies should further explore the treatments identified in this review to expand the evidence base in this relatively underexplored field.

Systemic Factors Affecting Pain Management in Dentistry

There are several factors that affect a patient's experience of pain. These include both local and systemic factors. The systemic factors that affect patients' dental and orofacial pain experience include, but not limited to, hormonal, nutritional, systemic infections, neurodegenerative, and autoimmune, among others. Comprehensive medical history is essential to delineate any possible systemic factors affecting pain experience. A thorough review of systems should form the foundation, since multiple factors can affect the prognosis of pain management. This would facilitate early recognition and trigger prompt referrals to the appropriate medical professionals. This helps to reduce the health care burden.

Severe acute respiratory syndrome coronavirus 2 pathology and cell tropism in tongue tissues of COVID-19 autopsies

Since 2019, Coronavirus Disease 2019(COVID-19) has affected millions of people worldwide. Except for acute respiratory distress syndrome, dysgeusis is also a common symptom of COVID-19 that burdens patients for weeks or permanently. However, the mechanisms underlying taste dysfunctions remain unclear. Here, we performed complete autopsies of five patients who died of COVID-19. Integrated tongue samples, including numerous taste buds, salivary glands, vessels, and nerves were collected to map the pathology, distribution, cell tropism, and receptor distribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the tongue. Our results revealed that all patients had moderate lymphocyte infiltration around the salivary glands and in the lamina propria adjacent to the mucosa, and pyknosis in the epithelia of taste buds and salivary glands. This may be because the serous acini, salivary gland ducts, and taste buds are the primary sites of SARS-CoV-2 infection. Multicolor immunofluorescence showed that SARS-CoV-2 readily infects Keratin (KRT)7+ taste receptor cells in taste buds, secretory cells in serous acini, and inner epithelial cells in the ducts. The major receptors, angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine subtype 2 (TMPRSS2), were both abundantly expressed in these cells. Viral antigens and receptor were both rarely detected in vessels and nerves. This indicates that SARS-CoV-2 infection triggers pathological injury in the tongue, and that dysgeusis may be directly related to viral infection and cellular damage.

Long COVID-19 gastrointestinal related disorders and traditional Chinese medicine: A network target-based approach

The significant number of individuals impacted by the pandemic makes prolonged symptoms after COVID-19 a matter of considerable concern. These are numerous and affect multiple organ systems. According to the World Health Organization (WHO), prolonged gastrointestinal issues are a crucial part of post-COVID-19 syndrome. The resulting disruption of homeostasis underscores the need for a therapeutic approach based on compounds that can simultaneously affect more than one target/node. The present review aimed to check for nutraceuticals possessing multiple molecular mechanisms helpful in relieving Long COVID-19-specific gastrointestinal symptoms. Specific plants used in Keywords Chinese Medicine (TCM) expected to be included in the WHO Global Medical Compendium were selected based on the following criteria: (1) they are widely used in the Western world as natural remedies and complementary medicine adjuvants; (2) their import and trade are regulated by specific laws that ensure quality and safety (3) have the potential to be beneficial in alleviating intestinal issues associated with Long COVID-19. Searches were performed in PubMed, Elsevier, Google Scholar, Scopus, Science Direct, and ResearchGate up to 2023. Cinnamomum cassia, Glycyrrhiza uralensis, Magnolia officinalis, Poria cocos, Salvia miltiorrhiza, Scutellaria baicalensis, and Zingiber officinalis were identified as the most promising for their potential impact on inflammation and oxidative stress. Based on the molecular mechanisms of the phytocomplexes and isolated compounds of the considered plants, their clinical use may lead to benefits in gastrointestinal diseases associated with Long COVID-19, thanks to a multiorgan and multitarget approach.

Non-pharmacological strategies to alleviate dysgeusia in patients undergoing chemotherapy: A systematic review

PURPOSE

Dysgeusia is a common side effect in oncology patients, significantly impacting their quality of life. This systematic review aims to evaluate the effectiveness of non-pharmacological strategies in treating dysgeusia in patients undergoing chemotherapy or radiotherapy.

METHODS

Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a comprehensive literature search across five databases: PubMed, Embase, Cochrane Library, CINAHL, and the British Nursing Database. We used the Joanna Briggs Institute Critical Appraisal Tools to assess the quality of the included studies. A harvest plot was used to synthesise evidence about the differential effects of population-level interventions.

RESULTS

Nine studies of non-pharmacological strategies to manage dysgeusia were included. These studies encompassed a variety of interventions, including oral applications and supplements, instrumental techniques, and educational programs. The review identified promising interventions such as cryotherapy and Miraculine supplementation, which showed potential in mitigating taste alterations. Instrumental techniques like photobiomodulation therapy and complementary and integrative medicine approaches, including acupuncture and herbs, were also found to be beneficial. Educational and self-management strategies emerged as effective interventions for empowering patients to manage dysgeusia. Despite the diversity of interventions and the limitations of the included studies, such as small sample sizes and geographical differences, these findings underscore the potential of non-pharmacological strategies in managing dysgeusia.

CONCLUSION

The results support the integration of these strategies into clinical practice, highlighting the importance of multidisciplinary approaches to improve patient care. Further research should prioritize rigorous studies to enhance evidence and explore long-term effects.

Factors associated with older adults' cognitive decline 6 months after gamma-variant SARS-CoV-2 infection

Background

Cognitive deficits are commonly reported after COVID-19 recovery, but little is known in the older population. This study aims to investigate possible cognitive damage in older adults 6 months after contracting COVID-19, as well as individual risk factors.

Methods

This cross-sectional study involved 70 participants aged 60-78 with COVID-19 6 months prior and 153 healthy controls. Montreal Cognitive Assessment-Basic (MoCA-B) screened for cognitive impairment; Geriatric Depression Scale and Geriatric Anxiety Inventory screened for depression and anxiety. Data were collected on demographics and self-reports of comorbid conditions.

Results

The mean age of participants was 66.97 ± 4.64 years. A higher proportion of individuals in the COVID group complained about cognitive deficits (χ2 = 3.574; p = 0.029) and presented with deficient MoCA-B scores (χ2 = 6.098, p = 0.014) compared to controls. After controlling for multiple variables, all the following factors resulted in greater odds of a deficient MoCA-B: COVID-19 6-months prior (OR, 2.44; p = 0.018), age (OR, 1.15; p < 0.001), lower income (OR, 0.36; p = 0.070), and overweight (OR, 2.83; p = 0.013). Further analysis pointed to individual characteristics in COVID-19-affected patients that could explain the severity of the cognitive decline: age (p = 0.015), lower income (p < 0.001), anxiety (p = 0.049), ageusia (p = 0.054), overweight (p < 0.001), and absence of cognitively stimulating activities (p = 0.062).

Conclusion

Our study highlights a profile of cognitive risk aggravation over aging after COVID-19 infection, which is likely mitigated by wealth but worsened in the presence of overweight. Ageusia at the time of acute COVID-19, anxiety, being overweight, and absence of routine intellectual activities are risk factors for more prominent cognitive decline among those infected by COVID-19.

Demographic and clinical characteristics of patients with zinc deficiency: analysis of a nationwide Japanese medical claims database

Zinc deficiency, affecting more than 2 billion people globally, poses a significant public health burden due to its numerous unfavorable effects, such as impaired immune function, taste and smell disorders, pneumonia, growth retardation, visual impairment, and skin disorders. Despite its critical role, extensive large-scale studies investigating the correlation between patient characteristics and zinc deficiency still need to be completed. We conducted a retrospective, cross-sectional observational study using a nationwide Japanese claims database from January 2019 to December 2021. The study population included 13,100 patients with available serum zinc concentration data, excluding individuals under 20 and those assessed for zinc concentrations after being prescribed zinc-containing medication. Significant associations with zinc deficiency were noted among older adults, males, and inpatients. Multivariate analysis, adjusting for age and sex, indicated significant associations with comorbidities, including pneumonitis due to solids and liquids with an adjusted Odds Ratio (aOR) of 2.959; decubitus ulcer and pressure area (aOR 2.403), sarcopenia (aOR 2.217), COVID-19 (aOR 1.889), and chronic kidney disease (aOR 1.835). Significant association with medications, including spironolactone (aOR 2.523), systemic antibacterials (aOR 2.419), furosemide (aOR 2.138), antianemic preparations (aOR 2.027), and thyroid hormones (aOR 1.864) were also found. These results may aid clinicians in identifying patients at risk of zinc deficiency, potentially improving care outcomes.

The Influence of COVID-19 in Endocrine Research: Critical Overview, Methodological Implications and a Guideline for Future Designs

The COVID-19 pandemic has changed many aspects of people's lives, including not only individual social behavior, healthcare procedures, and altered physiological and pathophysiological responses. As a result, some medical studies may be influenced by one or more hidden factors brought about by the COVID-19 pandemic. Using the literature review method, we are briefly discussing the studies that are confounded by COVID-19 and facemask-induced partiality and how these factors can be further complicated with other confounding variables. Facemask wearing has been reported to produce partiality in studies of ophthalmology (particularly dry eye and related ocular diseases), sleep studies, cognitive studies (such as emotion-recognition accuracy research, etc.), and gender-influenced studies, to mention a few. There is a possibility that some other COVID-19 related influences remain unrecognized in medical research. To account for heterogeneity, current and future studies need to consider the severity of the initial illness (such as diabetes, other endocrine disorders), and COVID-19 infection, the timing of analysis, or the presence of a control group. Face mask-induced influences may confound the results of diabetes studies in many ways.

Lipopolysaccharide increases bitter taste sensitivity via epigenetic changes in Tas2r gene clusters

T2R bitter receptors, encoded by Tas2r genes, are not only critical for bitter taste signal transduction but also important for defense against bacteria and parasites. However, little is known about whether and how Tas2r gene expression are regulated. Here, we show that in an inflammation model mimicking bacterial infection using lipopolysaccharide, the expression of many Tas2rs was significantly upregulated and mice displayed markedly increased neural and behavioral responses to bitter compounds. Using single-cell assays for transposase-accessible chromatin with sequencing (scATAC-seq), we found that the chromatin accessibility of Tas2rs was highly celltype specific and lipopolysaccharide increased the accessibility of many Tas2rs. scATAC-seq also revealed substantial chromatin remodeling in immune response genes in taste tissue stem cells, suggesting potential long-lasting effects. Together, our results suggest an epigenetic mechanism connecting inflammation, Tas2r gene regulation, and altered bitter taste, which may explain heightened bitter taste that can occur with infections and cancer treatments.

Salt Taste and Salt Sensitive Hypertension in HIV

PURPOSE OF REVIEW

To provide a summary of current literature and propose potential mechanistic models to help us understand the role of HIV infection/antiretroviral therapy (ART), salt taste sensitivity (STS), and salt sensitivity of blood pressure (SSBP) in hypertension development.

RECENT FINDINGS

The epithelial sodium channel (ENaC) is the main protein/sodium channel for recognizing Na + in the tongue and mediates preference to low-medium salt concentrations in animals and humans. Considering the pressor response to oral salt in individuals with SSBP, poor STS may worsen blood pressure. Specific genetic variants in ENaC are linked to salt taste perception and hypertension. HIV infection, some ART, and specific antihypertensive drugs are associated with reduced STS and an increased liking for salty foods. Persons with HIV (PWH) on ART may have a decreased STS and are at a higher risk of developing salt-sensitive hypertension. Inflammation mediated by dietary salt is one of the drivers of poor STS and salt-sensitive hypertension among PWH.

[Mechanisms and Management of COVID-19-Associated Taste Disorders]

The taste buds in the human tongue contain specialized cells that generate taste signals when they are stimulated. These signals are then transmitted to the central nervous system, allowing the human body to distinguish nutritious substances from toxic or harmful ones. This process is critical to the survival of humans and other mammals. A number of studies have shown that dysgeusia, or taste disorder, is a common complication of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which can severely affect patients' nutritional intake and quality of life. Based on the physiological process of taste perception, the direct causes of dysgeusia include dysfunction of taste receptors and damage to the taste nervous system, while indirect causes include genetic factors, aging-related changes, bacterial and viral infections, and cancer treatments such as radiotherapy and chemotherapy. The pathogenic factors of dysgeusia are complicated, further research is needed to fully understand the underlying mechanisms, and some of the reported findings and conclusions still need further validation. All these form a great challenge for clinical diagnosis of the cause and targeted treatment of dysgeusia. Herein, we reviewed published research on the physiological process of taste perception, the potential mechanisms of taste disorders related to SARS-CoV-2 infection, and strategies for prevention and treatment, providing theoretical support for establishing and improving the comprehensive management of COVID-19 complicated by taste disorders.

Inflammation induces bitter taste oversensitization via epigenetic changes in Tas2r gene clusters

T2R bitter receptors, encoded by Tas2r genes, are not only critical for bitter taste signal transduction but also important for defense against bacteria and parasites. However, little is known about whether and how Tas2r gene expression are regulated. Here we show that, in an inflammation model mimicking bacterial infection, the expression of many Tas2rs are significantly up-regulated and mice displayed markedly increased neural and behavioral responses to bitter compounds. Using single-cell assays for transposase-accessible chromatin with sequencing (scATAC-seq), we found that the chromatin accessibility of Tas2rs was highly cell type specific and inflammation increased the accessibility of many Tas2rs . scATAC-seq also revealed substantial chromatin remodeling in immune response genes in taste tissue stem cells, suggesting potential long-term effects. Together, our results suggest an epigenetic mechanism connecting inflammation, Tas2r gene regulation, and altered bitter taste, which may explain heightened bitter taste that can occur with infections and cancer treatments.

Clinical Features of COVID-19 and Differentiation from Other Causes of CAP

Community-acquired pneumonia (CAP) is a significant cause of morbidity and mortality, one of the most common reasons for infection-related death worldwide. Causes of CAP include numerous viral, bacterial, and fungal pathogens, though frequently no specific organism is found. Beginning in 2019, the COVID-19 pandemic has caused incredible morbidity and mortality. COVID-19 has many features typical of CAP such as fever, respiratory distress, and cough, and can be difficult to distinguish from other types of CAP. Here, we highlight unique clinical features of COVID-19 pneumonia such as olfactory and gustatory dysfunction, lymphopenia, and distinct imaging appearance.

[Olfactory, gustatory and auditory disorders associated with COVID-19. A systematic review of their distribution and pathogenesis]

The presented systematic review contains basic information about the frequency, characteristic features of the course and pathogenesis of olfactory, gustatory and auditory disorders that occur with COVID-19, with which an otorhinolaryngologist meets in his practice. These disorders are often the first, and sometimes the only, manifestations of the underlying disease, which determines their role in early diagnosis and timely detection of the underlying disease. The article includes original articles, clinical case reports and literary reviews.

Characterization of Metallic Off-Flavors in Drinking Water: Health, Consumption, and Sensory Perception

Characterization of taste- and flavor-producing metals, namely iron and copper, in drinking water is a multifaceted subject. Both metals are essential nutrients, can be toxic, and are known to produce unpleasant tastes and flavor sensations in drinking water. Ingestion of trace metal contaminants through drinking water is a probable source of human exposure. Biochemical mechanisms of metallic flavor perception have been previously described; however, less is known about how variations in salivary constituents might impact individuals' sensitivities to metallic flavors and beverage consumption behaviors. This research presents findings from in vitro experiments, using artificial human saliva, to better understand the role of salivary lipids and proteins on metallic flavor production as measured by biomarkers of metal-induced oxidative stress. The results indicate that metal-induced lipid oxidation, as measured by thiobarbituric acid reactive substances (TBARS), is dominated by salivary proteins, is slightly inhibited in the presence of salivary nitrite, and is detectable by the TBARS method at and above respective concentrations of 9 µM (0.5 mg/L) and 90 µM (5 mg/L), which are both above the aesthetic standards for iron (0.3 mg/L) and copper (1.0 mg/L) in drinking water. Preliminary study with human subjects indicated that reduction in metallic flavor sensitivity, as measured by the best estimate flavor threshold for ferrous iron among 33 healthy adults aged 19-84 years old (22 females), corresponded with reduced drinking water consumption and increased caloric beverage intake among older subjects (>60 years), as determined by a validated self-reported beverage intake questionnaire. These findings provide insights for further research to examine how salivary constituents can impact humans' sensory abilities in detecting metallic off-flavors in water, and how reduced metallic flavor sensitivity may influence beverage choices and drinking water consumption.

Smell and Taste Function and Their Disturbances in Sjögren's Syndrome

Chemosensory disorders are a possible disturbance in Sjögren's syndrome (SS). The aim of the study is to comprehensively present chemosensory disorders in SS and to indicate their possible causes. The possible causes of taste and smell disorders in SS are changes in the structure of exocrine glands and their dysfunction, damage to receptors and weakening of their ability to regenerate, and neurological changes in the form of peripheral neuropathy and impaired cognitive function. Other postulated causes of chemosensory disorders are autoimmune mechanisms, adverse effects of drugs used in SS, and primary potentially SS-triggering viral infections. They are multifactorial and may occur independently of each other. The time of their onset and correlation with other disease symptoms may facilitate the determination of their primary cause in each patient. Awareness of chemosensory disorders in SS may help to ease their progress and eliminate other factors responsible for their more severe manifestation. In the prevention and treatment of chemosensory disorders in SS, the most important thing is to alleviate xerostomia and dryness in the nasal cavity and their effects in the form of chronic local inflammations, counteract receptor atrophy, and an implementation of appropriate neurological diagnosis and treatment.

Gustatory dysfunction and oral ulceration in COVID-19 patients: A cross sectional study

Background

Over the past year, patients infected by severe acute respiratory syndrome coronavirus-2 presented with severe gustatory dysfunction, the prevalence of which varies among different populations. Furthermore, there have been sporadic reports of oral ulceration observed in coronavirus disease-19 (COVID-19) patients due to varied reasons. The aim of this study was to investigate and characterize the presence of gustatory disorders, oral ulceration, and other oral changes in patients with laboratory-confirmed COVID-19 infection.

Materials and Methods

In this cross-sectional observational study, a total of 402 participants who were detected COVID-19 positive by reverse transcription-polymerase chain reaction were included. Their demographic and clinical data were recorded through hospital records. The participants were interviewed either in person or on the telephone to record any change in taste and/or changes within the oral cavity. t-test for independent means was used to compare mean age, while other characteristics were compared by Chi-square test and Z-score test. P < 0.05 was taken as significant.

Results

Out of the total sample of 402 individuals, 262 were male and 140 were female. The prevalence of gustatory dysfunction and oral ulceration was 43.53% and 15.67%, respectively, in the studied sample. Significantly more females had gustatory dysfunction than males and older subjects more commonly than younger. The symptom of loss/change of taste and oral ulceration were more probable to occur together. In addition, the tongue was the most common site for ulceration in our studied sample.

Conclusion

Loss of taste is a common symptom of COVID-19 patients, whereas oral ulceration is not so commonly reported. However, the presence of both these symptoms could impair the quality of life of patients and hamper adequate nutritional uptake.