Prevalence of taste and smell dysfunction in mild and asymptomatic COVID-19 patients during Omicron prevalent period in Shanghai, China: a cross-sectional survey study

Characteristics of patients with COVID-19 and smell and/or taste disorders depending on different virus strains: a cross-sectional study in Hiroshima, Japan

OBJECTIVE

The purpose of the study is to compare the prevalence and associated risk factors of smell and/or taste disorders depending on different virus strains in Hiroshima, Japan.

DESIGN

A cross-sectional design was used.

SETTING AND PARTICIPANTS

Data were collected for all COVID-19-confirmed inpatients admitted to 27 hospitals in Hiroshima prefecture, Japan, between 8 April 2020 and 31 January 2023.

MAIN OUTCOME MEASURES

Smell and/or taste disorders were indicated by physicians on Hiroshima prefecture COVID-19 version J-SPEED forms completed at discharge.

RESULTS

The COVID-19 data from this period corresponds to the following four strains: Wild-dominant, Alpha-dominant, Delta-dominant and Omicron-dominant. A total of 11 353 confirmed cases were analysed and 1261 cases (11.11%) were reported for smell and/or taste disorders.Among patients with Wild-dominant, 241 out of 1141 cases (21.12%) exhibited smell and/or taste disorders. For Alpha, 223 out of 1265 cases (17.63%), for Delta, 480 out of 1516 cases (31.66%) and for Omicron, 317 out of 7431 cases (4.27%) presented with smell and/or taste disorders. For all four variants, age<65 (Wild: adjusted odds ratio [aOR]=2.66, 95% confidence interval [CI]:1.82-3.88; Alpha:aOR=2.00, 95%CI:1.39-2.88; Delta: aOR=2.42, 95%CI:1.54-3.81; Omicron: aOR=1.84, 95%CI:1.40-2.42) were related to smell and/or taste disorders. For the Wild and Delta variants, higher odds of reporting smell and/or taste disorders were found among wmen (Wild:aOR=1.63, 95%CI:1.20-2.22; Delta: aOR=1.41, 95%CI:1.10- 1.80).

CONCLUSIONS

The proportion of patients with smell and/or taste disorders varied significantly depending on the virus strain. Our findings indicate that the Delta-dominant period had the highest number of patients with these disorders, while the Omicron-dominant period had the lowest. Moreover, our study identified risk factors for smell and/or taste disorders for each variant.

Effect of oral zinc and steroids on long COVID hyposmia and hypogeusia

Objective

We studied the prognosis of olfactory and gustatory dysfunctions in patients with long COVID (Coronavirus Disease 2019) after treatment with oral zinc and steroids.

Methods

We measured olfactory and gustatory functions of long COVID patients at their first visits, and after 2-4 months of treatment with oral zinc and steroids using the traditional Chinese version of the University of Pennsylvania Smell Identification Test and the Waterless Empirical Taste Test. We also assessed by phone the recovery of olfactory and gustatory functions at a mean of about 10 months of follow-up.

Results

Among our 71 long COVID patients, 34 complained of loss of smell and taste. Their objective test results showed 88.2% hyposmic, 23.5% hypogeusic at the first visit. After treatment, 77.8% of the patients were hyposmic, and 16.7% were hypogeusic. After a mean follow-up of 10.35 months, 91.2% of the patients reported improvement in their olfactory function. Among the 36 patients who had complained only of smell loss, the objective test results showed 75% hyposmic at their first visit. After treatment, 71.4% of the patients were hyposmic. After a mean of 10.42 months of follow-up, 77.8% of the patients reported improvement in their olfactory function. Only one patient complained of taste loss.

Conclusions

We found that olfactory dysfunction in most long COVID patients persisted for more than 10 months.

An Explanation for Reports of Increased Prevalence of Olfactory Dysfunction With Omicron: Asymptomatic Infections

The prevalence of olfactory dysfunction (OD) in people infected with the Omicron variant is substantially reduced compared with previous variants. However, 4 recent studies reported a greatly increased prevalence of OD with Omicron. We provide a likely explanation for these outlier studies and reveal a major methodological flaw. When the proportion of asymptomatic infections is large, studies on the prevalence of OD will examine and report predominantly on nonrepresentative cohorts, those with symptomatic subjects, thereby artificially inflating the prevalence of OD by up to 10-fold. Estimation of the true OD prevalence requires representative cohorts that include relevant fractions of asymptomatic cases.

Camera-based visual feedback learning aid for recovering sense of smell and taste in COVID-19 survivors: a proof-of-concept study

Introduction

A significant proportion of people report persistent COVID-19-related anosmia, hyposmia or parosmia, often accompanied with ageusia, hypogeusia or dysgeusia. Here, we present a proof-of-concept study that assessed the feasibility and acceptability of a new Camera-Based Visual Feedback Learning Aid (CVFLA) and explored its potential to restore or improve persistent COVID-19-related smell and/or taste impairment.

Methods

Fifteen adult participants with persistent smell and/or taste impairment were randomly allocated to 7-, 14-, or 21-days baseline of symptom monitoring before receiving the intervention in up to 10 sessions (length and frequency determined by participant's preference and progress) using a specialised CVFLA apparatus (patent no. 10186160). Smell and taste were assessed pre- and post-intervention subjectively, and also objectively using the ODOFIN Taste Strips and Sniffin Sticks. Participant feedback about their experience of receiving CVFLA was obtained via a semi-structured interview conducted by someone not involved in delivering the intervention.

Results

The intervention was extremely well received, with no dropouts related to the intervention. There was also a significant improvement in smell and taste from pre- to post-CVFLA intervention (mean number of sessions = 7.46, SD = 2.55; total duration = 389.96 min, SD = 150.93) both in subjective and objective measures. All participants, except one, reported experiencing some improvement from the 2nd or 3rd session.

Discussion

This new CVFLA intervention shows promise in improving COVID-19 related impairment in smell and taste with a very high level of acceptability. Further studies with larger samples are required to confirm its potential in restoring, improving or correcting smell and/or taste impairment in relevant clinical and non-clinical groups.