Parosmia in patients with COVID-19 and olfactory dysfunction

Comparison of Patient Characteristics and Olfactory Sensitivity for Trigger Odorants in Parosmia and Phantosmia

OBJECTIVES

This study aimed to determine the characteristics of patients with qualitative olfactory dysfunction (qualOD) and whether individuals with parosmia exhibit increased olfactory sensitivity to previously reported odorous triggers of parosmia.

METHODS

This study included individuals aged ≥18 years, divided into quantitative OD only, parosmia, and phantosmia groups. Data collected included: clinical-demographic data, "Sniffin' Sticks" scores, questionnaires (depression scale, importance of olfaction), and information about parosmia and phantosmia. A proportion of patients underwent trigger odor threshold testing for 2-Furfurylthiol [FFT] found in coffee and 2,6-nonadienal [Nonadienal] found in cucumber.

RESULTS

Those with parosmia were typically younger women, with shorter OD duration due to post-viral OD (PVOD), hyposmic/normosmic, and experienced parosmia more severely. Parosmia was 3.5 times more likely in PVOD. Those with phantosmia were older, with longer OD duration due to idiopathic OD, hyposmic/anosmic, and experienced phantosmia less severely. There were no significant differences between FFT and Nonadienal threshold scores in patients with parosmia, phantosmia, or only quantitative OD, but all groups had significantly increased olfactory sensitivity for trigger odors compared to phenyl ethyl alcohol (PEA).

CONCLUSION

Parosmia and phantosmia patients have distinct characteristics. This may provide clinicians with a better understanding of possible olfactory outcomes in these patients. The higher olfactory sensitivity of all groups to trigger odors compared to PEA raises interesting points about parosmia triggers and odors in the context of warning for danger, in relation to the pathophysiology of parosmia that may be worth exploring in future studies.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:3277-3285, 2024.

Subjective Smell Disturbances in Children with Sars-Cov-2 or Other Viral Infections do not Correspond with Olfactory Test Results

BACKGROUND

Olfactory dysfunction associated with SARS-CoV-2 infection in children has not been verified by a validated olfactory test. We aimed to determine whether these complaints are objectifiable (test-based hyposmia), how often they occur during acute SARS-CoV-2 infection compared to other upper respiratory tract infections (URTI), as well as in children recovered from COVID-19 compared to children with long COVID.

METHODS

Olfactory testing (U-sniff test; hyposmia<8 points) and survey-based symptom assessments were performed in 434 children (5-17 years; 04/2021-06/2022). 186 symptom-free children served as controls. Of the children with symptoms of acute respiratory tract infection, SARS-CoV-2 PCR test results were positive in 45 and negative in 107 children (URTI group). Additionally, 96 children were recruited at least 4 weeks (17.6±15.2 weeks) after COVID-19, of whom 66 had recovered and 30 had developed long COVID.

RESULTS

Compared to controls (2.7%), hyposmia frequency was increased in all other groups (11-17%, p<0.05), but no between-group differences were observed. Only 3/41 children with hyposmia reported complaints, whereas 13/16 children with complaints were normosmic, with the largest proportion being in the long-COVID group (23%, p<0.05).

CONCLUSION

Questionnaires are unsuitable for assessing hyposmia frequency in children. Olfactory complaints and hyposmia are not specific for SARS-CoV-2 infection. The number of complaints in the long-COVID group could result from aversive olfactory perception, which is undetectable with the U-sniff test.

Depression, anxiety, and suicidal ideation in adults with COVID-induced parosmia

KEY POINTS COVID-induced parosmia is associated with anxiety, depression, and suicidal ideation. Parosmic patients have low rates of treatment benefit and little hope for improvement. Hyposmia may mitigate the quality-of-life burden in patients with parosmia.

[Subjective and objectified smell and taste disorders from an ENT post-Covid-19 consultation]

INTRODUCTION

Olfactory disorders are among the four most common post-COVID-19 complaints. The aim of our prospective study from a university ENT post-COVID consultation (PCS) was to substantiate the symptoms with psychophysical test results.

METHODS

After an ENT examination, 60 post-COVID-19 patients (41 women) were asked in writing about their medical history. Their ability to smell was tested using the extended Sniffin' Sticks test battery and their ability to taste was determined using the 3-drop test. From these data, three quantitative olfactory (RD) and gustatory (SD) diagnoses could be defined from normal value tables. Every second patient took part in a control examination.

RESULTS

Up to the first examination, 60 patients reported smell and 51 taste disorders; their average duration was 11 months in both cases. Objectified pathologic RD and SD had 87% and 42% of the total cohort, respectively. Every third patient suffered from an objectified combination of olfactory and gustatory damage. About every second patient complained of parosmia. Parosmic patients with two visits came earlier for a check-up. Six months after the initial examination, the detection thresholds, the TDI and the RD had improved in these patients. The self-assessment of olfactory ability had not changed.

CONCLUSIONS

Objectified pathologic RD persisted in our PCS for a mean of 1.5 years from the onset of infection. Parosmics had a better prognosis. For the healthcare system and especially for the patients affected, they continue to be a burden even after the pandemic.

BMI Increases in Individuals with COVID-19-Associated Olfactory Dysfunction

(1) Background: Reports suggest COVID-19-associated olfactory dysfunction (OD) may result in alterations in dietary behaviors and perceived weight change, but few studies using psychophysical evaluation of post-COVID-19-associated chemosensory dysfunction and body mass index (BMI) exist. The purpose of this study is to assess the impact of both quantitative and qualitative features of COVID-19-associated OD on BMI; (2) Methods: Recruitment of thirty-one participants with self-reported OD in the form of quantitative loss with and without qualitative features. Surveys with questions specific to qualitative olfactory function, Sniffin' Sticks tests, and BMI measures were completed at two visits, one year apart. Group differences were assessed with Wilcoxon signed-rank tests and the Holm-Bonferroni method; (3) Results: Individuals with persistent quantitative OD (n = 15) and self-reported parosmia (n = 19) showed statistically significant increases in BMI after 1 year (p = 0.004, adjusted α = 0.0125; p = 0.011, adjusted α = 0.0167). Controls with transient quantitative OD (n = 16) and participants without self-reported parosmia (n = 12) showed no statistically significant changes in BMI over the same time period (p = 0.079, adjusted α = 0.05; p = 0.028, adjusted α = 0.025); (4) Conclusions: This study shows an association between COVID-19-associated OD and BMI, suggesting olfaction may play a role in altering dietary habits and nutrition in this population. Larger study cohorts are needed to further evaluate this relationship.

The assessment of qualitative olfactory dysfunction in COVID-19 patients: a systematic review of tools and their content validity

Background

There is a lack of overview of the tools used to assess qualitative olfactory dysfunction, including parosmia and phantosmia, following COVID-19 illness. This could have an impact on the diagnosis and treatment offered to patients. Additionally, the formulations of symptoms are inconsistent and often unclear, and consensus around the wording of questions and responses is needed.

Aim of study

The aim of this systematic review is to provide an overview of tools used to assess qualitative olfactory dysfunction after COVID-19, in addition to addressing the content validity (i.e., item and response formulations) of these tools.

Methods

MEDLINE, Web of Science, and EMBASE were searched 5th of August 2022 and updated on the 25th of April 2023 to identify studies that assess qualitative olfactory dysfunction in COVID-19 patients. Primary outcomes were the tool used (i.e., questionnaire or objective test) and item and response formulations. Secondary outcomes included psychometric properties, study design, and demographic variables.

Results

The assessment of qualitative olfactory dysfunction is characterized by heterogeneity, inconsistency, and lack of validated tools to determine the presence and degree of symptoms. Several tools with overlapping and distinct features were identified in this review, of which some were thorough and detailed, while others were merely assessing the presence of symptoms as a binary measure. Item and response formulations are also inconsistent and often used interchangeably, which may lead to confusion, incorrect diagnoses, and inappropriate methods for solving the problem.

Conclusions

There is an unmet need for a reliable and validated tool for assessing qualitative olfactory dysfunction, preferably one that also captures quantitative olfactory issues (i.e., loss of smell), to ensure time-effective and specific assessment of the ability to smell. A consensus around the formulation of items and response options is also important to increase the understanding of the problem, both for clinicians, researchers, and the patient, and ultimately to provide the appropriate diagnosis and treatment.

Registration and protocol

The URL is https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=351621. A preregistered protocol was submitted and accepted (12.09.22) in the International prospective register of systematic reviews (PROSPERO) with the registration number CRD42022351621.

Human Nasal Epithelium Damage as the Probable Mechanism Involved in the Development of Post-COVID-19 Parosmia

Purpose

Since the beginning of the COVID-19 pandemic, understanding the physiopathological mechanisms of its manifestations has been crucial to understand the disease and its implications. As the disease evolved, post-infection complications have arisen such as olfactory dysfunctions including parosmia in which odourants are perceived in a distorted or an unpleasant way.

Methods

In this article, we attempt to clarify these mechanisms and the role of human nasal epithelium in the development of post-COVID-19 parosmia.

Results

The mechanisms by which SARS-CoV-2 generates olfactory dysfunction have not been elucidated, and multiple theories have been proposed pointing to the sustentacular cells of the olfactory epithelium as the main probable target of the virus.

Conclusion

Establishing the main physiopathological mechanism of post-COVID-19 parosmia will set a path for further investigations and determine treatment and preventive options for patients who have been reported to be extensively affected in multiple aspects of their lives such as eating habits and mental health.

The Correlation between the Results of the Sniffin' Sticks Test, Demographic Data, and Questionnaire of Olfactory Disorders in a Hungarian Population after a SARS-CoV-2 Infection

BACKGROUND

After a severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, smell disorders frequently occur, significantly affecting patients' quality of life (QoL).

METHODS

110 patients with persistent olfactory disorder after coronavirus infection were enrolled. These patients underwent chemosensory testing using the Sniffin' Sticks test, and completed the Questionnaire of Olfactory Disorders (QOD).

RESULTS

30% of the patients reported anosmia, and 70% reported hyposmia. Upon comparing subjective and chemosensory testing categories, good category matching was observed in 75.3% (i.e., anosmia based on both methods in 10 and hyposmia in 48 cases). Statistical analysis using the Chi-square test revealed a significant result (p = 0.001 *). Between the TDI (i.e., Threshold, Discrimination, Identification) results of the three subjective report groups (i.e., hyposmia, anosmia, and parosmia), no significant differences were observed. When the TDI and QOD results were compared, no consistent significant correlations were found in most TDI and QOD outcomes. Between the TDI and Scale 2 results, a significant, although slight correlation was observed by the Spearman's (rho = 0.213, p = 0.027 *) and Pearson's (rho = 0.201, p = 0.037 *) tests.

CONCLUSIONS

The nonsignificant correlation between objective and subjective methods suggests that these results should be interpreted independently. Moreover, adequate management is essential even in mild cases.

Olfactory dysfunction in COVID-19: new insights into the underlying mechanisms

The mechanisms of olfactory dysfunction in COVID-19 are still unclear. In this review, we examine potential mechanisms that may explain why the sense of smell is lost or altered. Among the current hypotheses, the most plausible is that death of infected support cells in the olfactory epithelium causes, besides altered composition of the mucus, retraction of the cilia on olfactory receptor neurons, possibly because of the lack of support cell-derived glucose in the mucus, which powers olfactory signal transduction within the cilia. This mechanism is consistent with the rapid loss of smell with COVID-19, and its rapid recovery after the regeneration of support cells. Host immune responses that cause downregulation of genes involved in olfactory signal transduction occur too late to trigger anosmia, but may contribute to the duration of the olfactory dysfunction.

Eating Habits and Body Weight Changes Induced by Variation in Smell and Taste in Patients with Previous SARS-CoV-2 Infection

Olfactory and gustatory dysfunction are recognized as common symptoms in patients with COVID-19, with a prevalence ranging, respectively, between 41-61% and 38.2-49%. This review focused on relating the variations in dietary habits with the reduction/loss of smell and/or taste in patients who contracted the COVID-19 infection. Primarily, we reviewed the main pathological mechanisms involved in COVID 19-induced anosmia/dysosmia and ageusia/dysgeusia. Then, we explored and summarized the behavioural changes in food intake and body weight during the COVID-19 pandemic in relation to sensory impairment and the underlying mechanisms. Most studies on this topic argue that the altered chemosensory perception (taste and smell) mainly induces reduced appetite, leading to a faster fullness sensation during the consumption of a meal and, therefore, to a decrease in body weight. On the other hand, a reduced perception of the food's sensory properties may trigger compensatory responses that lead some individuals to increase food intake with a different effect on body weight. Regarding body weight, most studies evaluated malnutrition in patients hospitalized for COVID-19; more studies are warranted to investigate nutritional status specifically in non-hospitalized patients with olfactory and gustatory dysfunctions caused by COVID-19 infection.

Clinical factors associated with lower health scores in COVID-19-related persistent olfactory dysfunction

BACKGROUND

Patients with persistent COVID-19 olfactory dysfunction (OD) commonly report parosmia. Understanding the impact of COVID-19 OD and parosmia is critical to prioritizing research and interventions. In this study we investigate the impact of parosmia and other clinical and disease characteristics on health state utility values (HUVs) for those with persistent COVID-19 OD.

METHODS

Patients with a history of COVID-19 diagnosis and persistent OD were recruited from a tertiary medical center and a social media support forum for chemosensory dysfunction. Clinical characteristics and disease-specific symptoms were obtained along with self-reported history of smell function and presence of parosmia. HUVs were calculated using indirect (EuroQol 5-Dimension [EQ-5D]) and direct (VAS) measures.

RESULTS

Our study included 286 subjects (75.52% women) with persistent COVID-19-related OD. Results (mean ± standard deviation) of HUVs based on EQ-5D and VAS were 0.81 ± 0.14 and 0.73 ± 0.21, respectively. Mean self-reported smell function (on a 0-10 scale) was 9.67 ± 1.25 pre-COVID-19, 0.93 ± 2.34 at diagnosis, and 3.39 ± 2.32 at most current assessment. A total of 89.16% of the subjects reported parosmia and 24.13% sought medical care for anosmia. Seeing an MD for OD (p < 0.001), female gender (EQ-5D only, p = 0.002), a history of chronic pain (p < 0.05) and depression/anxiety (EQ-5D only, p < 0.001) predicted worse health. Parosmia and persistent symptoms, such as shortness of breath, were associated with lower EQ-5D and VAS scores, but did not independently predict poorer health scores on multivariable analysis.

CONCLUSION

Persistent COVID-19 OD results in health states comparable to other chronic diseases.

Phantosmia May Predict Long-Term Measurable Olfactory Dysfunction After COVID-19

Objectives

Persistent olfactory dysfunction (OD) after 6 months caused by SARS‐CoV‐2 infection has been reported with a variable prevalence worldwide. This study aimed to determine the prevalence of long‐term OD and identify predisposing factors.

Methods

A prospective cohort study was conducted on 100 adults with COVID‐19. Olfactory function was assessed with the University of Pennsylvania Smell Identification Test and a symptom survey at the onset of disease and 30 days later. Patients with persistent quantitative OD at the second assessment were reevaluated after 1 year. Demographic variables, symptoms, and the degree of smell loss were analyzed.

Results

Participants included 100 patients. The mean age was 42.2 ± 15.6 years, 55 (55%) were female, and 56 (56%) were outpatients. Baseline smell loss was identified in 75/100 (75%) patients, decreasing to 39/95 (40%) after 1 month, and persisting in 29 patients after 1 year. Phantosmia at baseline was the only risk factor identified for persistent OD after 1 year (relative risk 2.51; 95% confidence interval 1.53–4.12; p < 0.001). Regardless of the outcome in smell function, a significant decline in olfaction was associated with the presence of phantosmia at 1 month (β = −12.39; 95% CI −19.82 to −4.95; p < 0.01).

Conclusions

SARS‐CoV‐2 (2019–2020 variants) produced a highly frequent OD that persisted in 29% of the patients after 1 year. The presence of phantosmia at baseline and 1 month was associated with a worse evolution, but phantosmia may interfere with the performance in an identification smell test. A longer follow‐up is required in these patients.

Level of Evidence

2 Laryngoscope, 2022

Results from psychophysical tests of smell and taste during the course of SARS-CoV-2 infection: a review

Only a few studies have assessed smell and taste in Coronavirus Disease 2019 (COVID-19) patients with psychophysical tests, while the majority performed self-rating evaluations. Given the heterogeneity of the published literature, the aim of this review was to systematically analyse the articles on this topic with a focus on psychophysical testing. A search on PubMed and Web of Science from December 2019, to November 2021, with cross-references, was executed. The main eligibility criteria were English-language articles, investigating the clinical features of olfaction and gustation in COVID-19 patients using self-rating assessment, psychophysical testing and imaging techniques. A total of 638 articles were identified and 66 were included. Self-rating assessment was performed in 31 studies, while psychophysical testing in 30 and imaging techniques in 5. The prevalence of chemosensory dysfunction was the most investigated topic, followed by the recovery time. About the psychophysical assessment, the extended version of the Sniffin’ Sticks was used in 11 articles and the Connecticut Chemosensory Clinical Research Center test in another 11. The olfactory threshold performance was the most impacted compared to the discrimination and identification capacities in accordance with the hypothesis of a tropism of SARS-CoV-2 for the olfactory mucosa. The timing significantly influenced the results of the psychophysical testing with 20% of patients presenting olfactory dysfunction at one month after infection.

SARS-CoV-2 Leads to Significantly More Severe Olfactory Loss than Other Seasonal Cold Viruses

The aim of this study was to investigate whether COVID-associated olfactory impairment differs from olfactory disorders due to other upper respiratory tract infections. We investigated the frequency of a SARS-CoV-2 infection among subjects presenting with a subjective olfactory impairment to a corona outpatient clinic between October 2020 and March 2021. Olfactory and gustatory loss were tested psychophysically, and the type of infection, SARS-CoV-2 versus 14 other common cold viruses, was assessed with nasopharyngeal swabs. Differences between the smell impairment caused by the pathogens were compared. Out of the 2120 patients, 314 reported sudden smell and/or taste loss (14%). In 68.9% of them, olfactory and in 25.6%, gustatory dysfunction could be confirmed by psychophysical testing. Of those with a psychophysically determined loss of smell, 61% were tested positive for SARS-CoV-2. SARS-CoV-2 led to a significantly more severe loss of smell and more qualitative olfactory disorders than other pathogens. Apart from rhinorrhea, shortness of breath and sore throat accompanying cold symptoms do not differ significantly between the viruses indicating the particular importance of smell loss in the differential diagnosis of seasonal colds. Multiplex-PCR in non-COVID patients revealed that only 27% of them had rhinoviruses, whereas the remainder were no further identified pathogens. Olfactory screening significantly increases diagnostic accuracy in COVID-19 patients compared to subjective assessment of olfactory loss.

Patterns of self-reported recovery from chemosensory dysfunction following SARS-CoV-2 infection: insights after 1 year of the pandemic

BACKGROUND

The coronavirus disease (COVID-19), due to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), causes chemosensory dysfunction.

AIMS/OBJECTIVES

To determine the characteristics of chemosensory dysfunction and to identify factors associated with chemosensory complete recovery and time to recovery.

MATERIALS AND METHODS

This cross-sectional study included all patients presenting with chemosensory dysfunction and confirmed SARS-CoV-2 infection from May to August 2020 who underwent telemedicine follow-up after 1 year to assess their chemosensory recovery.

RESULTS

A total of 372 patients were included, of which 53.8% were male. The mean age ± SD was 37.45 ± 13.44. The majority experienced combined (olfactory and gustatory) dysfunction (85.7%), and 315 patients (84.7%) had complete loss of chemosensory function. The independent predictors associated with a low likelihood of complete recovery were parosmia (aOR 0.16, p < .001), upper respiratory tract symptoms (aOR 0.28, p = .001), and dyspnoea (aOR 0.21, p < .001), whereas the factors associated with a long recovery period were parosmia (aOR 12.04, p = .002), headache (aOR 7.19, p = .007), and hypertension (aOR 7.76, p = .039).

CONCLUSIONS

A full recovery outcome was predominant. The presence of parosmia was linked to both an incomplete recovery and a long time to recovery.

SIGNIFICANCE

Parosmia and respiratory symptoms are implicated in the incomplete recuperation of chemosensory function.

The Role of Social Media in Improving Patient Recruitment for Research Studies on Persistent Post-Infectious Olfactory Dysfunction

Background and Objectives: Since the COVID-19 pandemic, the number of cases of post-infectious olfactory dysfunction (PIOD) has substantially increased. Despite a good recovery rate, olfactory dysfunction (OD) becomes persistent in up to 15% of cases and further research is needed to find new treatment modalities for those patients who have not improved on currently available treatments. Social media has emerged as a potential avenue for patient recruitment, but its role in recruiting patients with smell dysfunction remains unexplored. We conducted a survey using the AbScent Facebook page to evaluate the feasibility of using this platform for future studies on smell dysfunction. Materials and Methods: Between 26 October and 4 November 2021, we conducted an online survey to evaluate propensity of patients with PIOD who would be willing to participate in research studies on smell dysfunction. Results: Sixty-five subjects were surveyed with a response rate of 90.7%. The median visual analogue scale (VAS) for sense of smell was 0 at infection and 2 at survey completion. The median length of OD was 1.6 years, and the main cause of OD was SARS-CoV-2 (57.6%). Parosmia was reported in 41 subjects (69.5%) whilst phantosmia in 22 (37.3%). The median length of olfactory training (OT) was 6 months but subjectively effective in 15 subjects (25.4%). Twenty-seven subjects (45.8%) tried other medications to improve olfaction, but only 6 participants (22.2%) reported an improvement. All subjects expressed their propensity to participate in future studies with most of them (38; 64.4%) willing to be enrolled either in medical and surgical studies or to be part of a randomised study design (11; 18.6%). Conclusions: Using the AbScent Facebook platform we successfully selected a population of subjects with persistent and severe OD that have failed to improve on available treatments and are willing to participate in further clinical trials.

Phantosmia, Parosmia, and Dysgeusia Are Prolonged and Late-Onset Symptoms of COVID-19

Deficiencies in smell and taste are common symptoms of COVID-19. Quantitative losses are well surveyed. This study focuses on qualitative changes such as phantosmia (hallucination of smell), parosmia (alteration of smell), and dysgeusia (alteration of taste) and possible connections with the adaptive immune system. Subjective experience of deficiency in taste and smell was assessed by two different questionnaires after a median of 100 and 244 days after first positive RT-PCR test. SARS-CoV-2-specific antibody levels were measured with the iFlash-SARS-CoV-2 assay. After 100 days a psychophysical screening test for olfactory and gustatory dysfunction was administered. 30 of 44 (68.2%) participants reported a chemosensory dysfunction (14 quantitative, 6 qualitative, 10 quantitative, and qualitative) during COVID-19, eleven (25.0%) participants (1 quantitative, 7 qualitative, 3 quantitative, and quantity) after 100 days, and 14 (31.8%) participants (1 quantitative, 10 qualitative, 3 quantitative and qualitative) after 244 days. Four (9.1%) participants, who were symptom-free after 100 days reported now recently arisen qualitative changes. Serological and T-cell analysis showed no correlation with impairment of taste and smell. In conclusion, qualitative changes can persist for several months and occur as late-onset symptoms months after full recovery from COVID-19-induced quantitative losses in taste and smell.

Olfactory-related Quality of Life Adjustments in Smell Loss during the Coronavirus-19 Pandemic

BACKGROUND

Previous studies provided the first evidence that the importance of olfaction decreases with the duration of olfactory dysfunction (OD).

OBJECTIVE

To evaluate differences in olfactory-related quality of life (QoL) between patients with new-onset and persistent smell loss (>4 weeks) during the coronavirus-19 (COVID-19) pandemic and patients with persistent postinfectious OD (PIOD) that were recruited before the pandemic.

METHODS

This was a retrospective study that included 149 patients with self-reported OD. The olfactory-related QoL was measured using the questionnaire of OD (QOD). The QOD measures the degree to which patients (i) adjust and cope with smell loss (QOD-positive statement [QOD-PS]), (ii) suffer from distorted odor perceptions (QOD-parosmia [QOD-PAR]), and (iii) suffer from smell loss in general (QOD-negative statement [QOD-NS]). Self-perceived chemosensory function, demographics, olfactory function, and duration of smell loss were evaluated. Analyses of variance were used to depict differences in QoL-outcomes between different OD groups.

RESULTS

All patients included during the COVID-19 pandemic reported an extensive loss of chemosensory functions of smell, taste, and flavor perception. Psychophysical retronasal screening testing showed olfactory impairments in more than half of these patients. One-way analysis of variance and posthoc tests revealed that the QOD-NS was significantly higher in the new-onset OD group than the PIOD group. At the same time, the QOD-PS score was significantly higher in the PIOD and the persistent COVID-19 OD group than in the new-onset OD group.

CONCLUSION

We showed that patients with persistent OD experienced better olfactory-related adjustment and lower QoL-impairment scores than those with recent-onset smell loss, suggesting that the olfactory-related QoL might change as a function of time after symptom onset.