Olfactory Training in COVID-19 Associated Loss of Smell

NCT05421221 | Completed

• 1 other identifier: 12732020
• Study Type: interventional
• Target: 70
• Locations: 1 country
• Sites: 1

Brief Summary

Olfactory dysfunction (OD) like hyposmia or anosmia has been realized as a common symptom or even cardinal sign of the disease and can be persisting after recovering. There are two different hypotheses on the pathogenesis of OD in past COVID-19: The central hypothesis, which speculates on neurotrophic abilities on olfactory receptors in the neuroepithelium, and the peripheral hypothesis, which speculates on damage of the sensory olfactory epithelium. Potential treatment strategies aim for the unique neural plasticity of the olfactory system and its potential for recovery. Clinical studies and case reports have shown a promising effect of olfactory training (OT) by frequent sniffing and/or exposure to odors 2-4 times a day for several weeks. The main objective of the study is to assess the effects of olfactory training in patients with COVID-19 related OD on:

1. 1.objective olfactory testing with the Sniffin' sticks test (identification and discrimination),
2. 2.subjective OD and its impact on the daily life,
3. 3.other clinical scales and questionnaires referring to OD-related mood and quality of life,
4. 4.gender differences in COVID-19 related OD. Approach / methods OT will be performed twice a day with a 4-odor training set for 12 weeks. Effects of OT on COVID-19 related OD will be measured with objective and subjective efficacy variables.

Conditions

COVID-19; Hyposmia

Outcome Measures

Primary Outcomes (1)

• primary endpoint

  changes between groups from baseline to week 12/termination visit regarding correct odor identification and discrimination

  12 weeks

Secondary Outcomes (6)

• Visual Analog Scale

  12 weeks

• Short-Form-36 Health Survey Questionnaire (SF-36)

  12 weeks

• Mood inventory

  12 weeks

• Hospital Anxiety and Depression Scale

  12 weeks

• Patient Progress and treatment response over time

  12 weeks

Study Arms (2)

olfactory training group

EXPERIMENTAL

12 weeks of olfactory traiing with Sniffin' sticks "Duftquartett".

Device: Sniffin' sticks Duftquartett

no olfactory training with natural history of the disease

NO INTERVENTION

natural history of the disease

Interventions

Sniffin' sticks Duftquartett DEVICE

4-odor training set over 12 weeks with Sniffin' sticks "Duftquartett"

olfactory training group

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• The subject is aged over 18 years;
• confirmed diagnosis of COVID-19 at least three months ago (history of positive PCR-testing required) or positive serum nucleocapsid antibody titer against SARS-CoV2;
• post-infectious COVID-19 related olfactory dysfunction persisting for at least three months with abnormal Sniffin' sticks test (\<13/16 items correct in the identification part);
• the patient is willing to undergo odor training over 12 weeks;
• written ICF is obtained.

You may not qualify if:

• History of olfactory dysfunction prior to COVID-19 infection due to other conditions e.g. status post traumatic brain injury, Parkinson's disease, allergic rhinitis, etc.;
• Nasal pathology not related to COVID-19 in the systematic otorhinolaryngological examination including endoscopy.
• the participant is pregnant

Sponsors & Collaborators

• Medical University Innsbruck: lead

Study Sites (1)

Medical University of Innsbruck

Innsbruck, Tyrol, 6020, Austria

Location

Related Publications (1)

• De Cleene N, Jagusch F, Schmutzhard J, Gottfried T, Peball M, Djamshidian A, Ellmerer P, Goebel G, Helbok R, Kindl P, Loffler-Ragg J, Weiss G, Seppi K, Heim B; SMELL study-group. Protocol for olfactory training in persisting COVID-19-associated loss of smell (SMELL): a monocentric randomised controlled trial conducted in Innsbruck. BMJ Open. 2025 May 27;15(5):e094027. doi: 10.1136/bmjopen-2024-094027.

  PMID: 40436445 DERIVED

MeSH Terms

Conditions

COVID-19; Anosmia

Condition Hierarchy (Ancestors)

Pneumonia, Viral; Pneumonia; Respiratory Tract Infections; Infections; Virus Diseases; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; RNA Virus Infections; Lung Diseases; Respiratory Tract Diseases; Olfaction Disorders; Sensation Disorders; Neurologic Manifestations; Nervous System Diseases; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Study Officials

• Beatrice Heim, MD PhD

  Medical University of Innsbruck

  STUDY CHAIR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: INVESTIGATOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: June 15, 2022
• First Posted: June 16, 2022
• Study Start: August 10, 2022
• Primary Completion: December 31, 2024
• Study Completion: December 31, 2024
• Last Updated: April 23, 2025

Record last verified: 2025-04

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL
• Time Frame: after publication of the primary data
• Access Criteria: data will be deposited in appropriate public repositories

Locations

AU (1)