Abstract

Background: To assess the prevalence of gustatory (taste) dysfunction in Long COVID-19 patients, along with the type of dysfunction and the time taken for its resolution.

Methods: This is a retrospective observational study based on patients presenting to a specialist smell clinic being run as a part of long COVID clinic in an ENT department in a regional hospital in UK. Out of all these patients presenting to this clinic, the ones with taste problems with or without smell problems were included in this study and analysed from electronic patient records. Their taste dysfunction was described along with the follow up period to look at the resolution of symptoms and the time taken for the resolution.

Results: 70% of the patients had hypogeusia, 22% had dysgeusia and 8% had ageusia. 52% of the patients showed partial resolution of taste dysfunction, 28 % showed complete resolution and 16% had no improvement in a follow up period of 29 months. Overall, the taste problems lasted for an average of 19.3 ± 7.51 months.

Conclusions: From our study, we concluded there is a significant burden of taste dysfunction among the long COVID patients in addition to the smell dysfunction, and despite slow recovery, many of the patients are expected to recover months after the initial infection. Nevertheless, this adds to the distress of the patient as they are unable to enjoy their food during this time which can have negative effects on the quality of life of these patients.

Keywords

Long COVID-19; Gustatory (taste) dysfunction

Introduction

The novel Coronavirus infection (COVID-19) was first identified in Wuhan China as a cluster of pneumonia of unknown origin in December 2019 and was initially known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [1]. The ongoing pandemic has been a cause of significant morbidity and mortality, not just in the acute phase of the disease but also as a cluster of symptoms which occur/persist after the acute phase now recognized as long COVID which has increased the overall burden of the disease. The term long COVID was first used by Perego in social media to denote persistence of symptoms weeks or months after initial SARS-CoV-2 infection and the term ‘long haulers’ was used by Watson and by Yong [2-4].

Problems with smell and taste became known as the initial symptoms of the disease from patient reports (reported first by the senior author, ENT UK press release, March 2020) [5] and soon enough they also become one of the dominant symptoms in the long COVID patients. The affected individuals can have their smell and taste affected in various ways-total loss of smell and/or taste (anosmia or ageusia), partial loss (hyposmia or hypogeusia), altered (parosmia/ cacosmia or dysgeusia) or even hallucinations (phantosmia or phantogeusia). Several theories have been suggested as the underlying mechanisms of this long-term chemosensory dysfunction, which has been defined as symptoms persisting more than 3 months after the initial infection [6].

Taste loss has often been described in studies as being indistinguishable from smell loss as ‘flavour’ is believed to be because of retro-nasal perception and hence smell loss invariably leading to taste loss [7]. Some researchers also believe that taste loss in COVID is often smell loss which is confused by the patients [8]. However recently a metanalysis concluded taste loss as an individual symptom in COVID-19 suggesting need for further research into mechanism and implications of taste loss in these patients [9].

Taste dysfunction negatively affects the patient’s quality of life and can be seriously detrimental to professions that rely on their sensation of taste. A recent meta-analysis has predicted that 5.6% and 4.4% of patients might develop long lasting self-reported smell and taste dysfunction post COVID-19 respectively [10]. Although there are many studies looking at the burden of olfactory dysfunction, selfreported taste dysfunction has not been evaluated separately in many of them. Hence, this study was undertaken to observe the prevalence and type of taste dysfunction and its impact as reported by patients’ presenting to an ongoing Smell Clinic being run as a part of Long COVID clinic.

Objective

• To assess the prevalence of taste dysfunction in long COVID-19 patients with smell dysfunction.

• To assess the type of taste dysfunction, its recovery and time taken for recovery in these patients.

Materials and Methods

This retrospective observational study in a sample size of 50 patients. This study was conducted as part of a specialist smell long Covid service in a regional hospital in UK over a 29-month period from October 2020 to March 2023.

All the data were entered on Excel sheet® and analysed. All the qualitative data was summarized in the form of numbers and percentage. All the quantitative data was summarised as Mean ± Standard deviation.

Inclusion criteria

All the patients of both genders, in the age group 16-70 years, presenting to the smell clinic with post-CO

Exclusion criteria

Patients below 16 years and above 70 years, patients only having smell problems and no taste problems, non-COVID related taste and smell problems and patients lost to follow up were excluded from the study.

This is a retrospective observational study carried out over a 29-month period from October 2020 to March 2023 in a special Long COVID Clinic for patients with smell and taste problems. 165 patients presented to this clinic with smell and/or taste problems. Out of these 33 patients were excluded as they did not have COVID related smell and/or taste problems. The present study group comprised of 50 patients who had post-COVID taste problems with or without smell problems. These patients identified as having Long COVID symptoms of taste dysfunction had complaints with their taste sensation for at least over 3 months.

A detailed history and thorough otolaryngological examination were carried out in all the patients to rule out any organic causes of taste dysfunction. All the information for this study was self-reported by the patients and was collected from electronic patient records.

Patients were then followed up to find out if there was a resolution of the taste problems. If the patient reported a resolution, they were divided into two groups based on partial or complete resolution. The time taken for partial or complete resolution was also noted. All this information was also analysed from electronic patient records.

Results

All the patients with long COVID taste dysfunction also had associated olfactory dysfunction.

Highest number of patients-42% with Long COVID-19 taste problems were in middle age (ages 45 to 60 years). The above 60- year age group had the fewest patients with taste problems- only 16% (Figure 1).

Figure 1: Image with Thyroid Transcription Factor (TTF-1) stain, the staining reaction is nuclear, demonstrating its pulmonary origin.

Out of all these patients with long COVID taste problems-64% were females and only 36% were males.

In terms of the type of the type of gustatory dysfunction- the patients described their subjective taste sensation in four ways

1. Ageusia-no taste sensation at all.

2. Hypogeusia-Varying degrees of decreased taste sensation.

3. Dysgeusia-Altered, often unpleasant taste sensation than what is expected from a food item.

4. Phantogeusia - Hallucination of taste sensation without consuming any food item.

Majority of the patients-70% of them had hypogeusia, 22% had dysgeusia and 8% had ageusia. None of the patients reported phantogeusia.

These patients were followed up until the end of the study period and the degree of resolution if present along with the time required for the resolution from the initial COVID infection was noted from the patient records.

52% of the patients showed a definite improvement in the symptoms but not completely cured and were categorized as having partial resolution. 28% of the patients had complete resolution of their taste problems. However, 16% of the patients showed no improvement at all since the start of their taste dysfunction.

On evaluating the time taken for resolution, the patients having complete resolution of taste problems by the end of the study period took 15.2 ± 6.36 months to show total resolution of symptoms. Whereas patients with partial resolution of symptoms took 18.65 ± 6.65 months to begin to show improvement in the taste problems.

Looking at the whole set of patients with long COVID taste dysfunction, overall, the taste problems lasted for 19.3 ± 7.51 months suggesting significant burden of taste problems in long COVID patients (Figure 2).

Figure 2: Time taken for resolution of taste dysfunction expressed as Mean+standard deviation.

Discussion

Although, COVID-19 has paved the way for a lot of research into loss of chemosenory perceptions of taste and smell, a lot of the research is still muddled with no definite biologic mechanisms yet proven. In some studies, the amount of the virus is saliva is has been directly linked to the quantity of taste loss; with higher levels of virus suggestive of more taste loss [11,12] although this observation is controversial [13]. Some other studies have shown that based on the expression pattern of ACE2 in the taste cells, these cells can be directly affected by the virus as ACE2 is the receptor protein responsible for transporting the virus into the cells; also TMPRSS2 is another protein present on the supporting cells in taste buds that is responsible for processing spike protein of the virus [14,15]. There may also be direct effects on the brain that contribute to taste loss [16].

In our study, long COVID taste dysfunction was more reported by middle aged and women. This is consistent with the systematic reviews and metanalysis by Hannum ME,et al. [9] who found a significantly higher smell and taste loss in females and middle age group. Similar to our study, this study also showed resolution of taste problems in 88% of the patients in the study within a 2-year period [17]. Our study demonstrated similar findings with partial or complete resolution of taste dysfunction seen at an average of 19.3 months.

However, this study also has its limitations like we only used patient reported levels of taste dysfunction without the use of any objective tests as these patient reports were the most feasible at least during the initial phase of COVID-19 pandemic. Although the sample size is small, the results are comparable to larger multi-centre studies and other meta-analysis and systematic reviews [9].

Nevertheless, this study hints at the burden of taste dysfunction in long COVID-19 patients as the problems with taste were often ignored pre-COVID. Even presently, majority of the studies focus on the smell dysfunction [18] and sometimes as taste problems being associated with smell dysfunction, however problems with taste dysfunction are equally if not more responsible for the quality of life of these patients.

Conclusions

From our study, we concluded there is a significant burden of taste dysfunction among the long COVID patients in addition to the smell dysfunction, and despite slow recovery, many of the patients are expected to recover months after the initial infection. Nevertheless, this adds to the distress of the patient as they are unable to enjoy their food during this time which can have negative effects on the quality of life of these patients.

Contributor and Guarantor Information

The corresponding author attests that all the listed authors meet the authorship criteria and that no others meeting the criteria have been omitted.

Competing Interests

None declared.

Funding

No funding sources.

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Article Information

Article Type: RESEARCH ARTICLE

Citation: Luhana M, Evans C, Kumar BN (2023) Taste Dysfunction in Long COVID- 19 Patients: An Observational Study. J Surg Open Access 9(2): dx.doi.org/10.16966/2470-0991.269

Copyright: © Luhana M, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Publication history: 

Received date: 22 Mar, 2023

Accepted date: 29 Mar, 2023

Published date: 12 Apr, 2023