The Effect of Olfactory Training in Patients With COVID-19 Induced Olfactory Dysfunction
SMELLT2022
1 other identifier
interventional
65
1 country
1
Brief Summary
Aim: The aim is to investigate the effect of olfactory training with essential oils versus olfactory training with placebo-oils in patients with COVID-19 induced olfactory dysfunction Study design: The study is a placebo-controlled randomized clinical trial with an intervention group and a control group. The intervention group receive four essential oils with scents of orange, lavender, clove, and peppermint. Patients in the control group receive a fragrance kit, consisting of the same containers, but with fragrance-free oils added. Both groups are instructed to smell each of the four oils for 30 seconds in the morning and evening, over a three-month intervention period. Patients are given a diary in which to record their olfactory training. The nurse or medical student instructing the patients in the training and performing the smell and taste tests is blinded. Study population: Patients referred to the Unit for Sense of Taste and Smell in the Department of Otorhinolaryngology Head \& Neck and Audiology at Rigshospitalet. Inclusion criteria:
- Impaired sense of taste and smell following COVID-19 \> 3 months
- Hyposmia (16.25-30.5) or anosmia (\<16) assessed by Sniffin' Sticks Olfactory Test for Threshold, Discrimination and Identification (TDI) performed in the Unit for Sense of Taste and Smell with or without parosmia based on medical history
- \> 18 years of age Exclusion criteria:
- Cause of hyposmia, anosmia or parosmia other than COVID-19
- Does not read or speak Danish
- Lack of compliance to perform daily olfactory training Procedures: \- TDI-test: To assess patients' sense of smell, the TDI-test with Sniffin' Sticks is used, which is a validated tool with normative data. Questionnaires: \- 'Taste and Smell Tool for Evaluation' is used to investigate quality of life related to impaired sense of taste and smell.
Trial Health
Trial Health Score
Automated assessment based on enrollment pace, timeline, and geographic reach
participants targeted
Target at P25-P50 for not_applicable covid19
Started Jun 2022
Longer than P75 for not_applicable covid19
1 active site
Health score is calculated from publicly available data and should be used for screening purposes only.
Trial Relationships
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Study Timeline
Key milestones and dates
Study Start
First participant enrolled
June 29, 2022
CompletedFirst Submitted
Initial submission to the registry
September 2, 2022
CompletedFirst Posted
Study publicly available on registry
September 14, 2022
CompletedPrimary Completion
Last participant's last visit for primary outcome
April 30, 2024
CompletedStudy Completion
Last participant's last visit for all outcomes
September 30, 2025
CompletedSeptember 23, 2024
September 1, 2024
1.8 years
September 2, 2022
September 19, 2024
Conditions
Keywords
Outcome Measures
Primary Outcomes (1)
Change in Extended Sniffin' Sticks Test score
Change in TDI score measured by Burghart Extended Sniffin' Sticks Test (TDI test). The TDI test, consists of a threshold test, a discrimination test, and an identification test. The results of the three subtests makes a total TDI score, where the minimum score is 1 and the maximum score is 48. A score \>30 indicates normal olfactory function, a score between 15-30 indicates hyposmia and a score \<15 indicates anosmia in the form of severely impaired or complete loss of olfaction.
3 months follow-up
Secondary Outcomes (1)
Change in Quality of Life
3 months follow-up
Study Arms (2)
Intervention group
EXPERIMENTALOlfactory training twice a day with essential oils
Control group
PLACEBO COMPARATOROlfactory training twice a day with fragrance-free oils
Interventions
Olfactory training twice daily with essential oils from Urtegaarden Aps with scents of orange, lavender, clove and peppermint. The olfactory training is performed every morning and evening, by smelling each of the oils for 30 seconds.
Olfactory training twice daily with fragrance-free oils from Urtegaarden Aps in the same four containers as the intervention group. The olfactory training is performed every morning and evening, by smelling each of the oils for 30 seconds.
Eligibility Criteria
You may qualify if:
- Olfactory dysfunction caused by COVID-19
- Hyposmia (16.25-30.5) or anosmia (\<16) with or without parosmia assessed by TDI test with Sniffin Sticks performed in the Unit for Sense of Taste and Smell
- \> 18 years of age
You may not qualify if:
- Cause of hyposmia, anosmia or parosmia other than COVID-19
- Does not read or speak Danish
- Lack of compliance to perform daily olfactory training
Contact the study team to confirm eligibility.
Sponsors & Collaborators
Study Sites (1)
Department of Otorhinolaryngology, Head and Neck Surgery & Audiology, Copenhagen University Hospital
Copenhagen, 2100, Denmark
Related Publications (1)
Mogensen DG, Aanaes K, Andersen IB, Jarden M, Backer V. Effect of Olfactory Training in COVID-19 Related Olfactory Dysfunction-A Placebo-Controlled Trial. Laryngoscope. 2025 Dec;135(12):4849-4857. doi: 10.1002/lary.32275. Epub 2025 May 15.
PMID: 40371997DERIVED
MeSH Terms
Conditions
Interventions
Condition Hierarchy (Ancestors)
Intervention Hierarchy (Ancestors)
Study Officials
- STUDY CHAIR
Vibeke G Backer, Professor
Rigshospitalet, Denmark
Central Study Contacts
Study Design
- Study Type
- interventional
- Phase
- not applicable
- Allocation
- RANDOMIZED
- Masking
- QUADRUPLE
- Who Masked
- PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
- Purpose
- TREATMENT
- Intervention Model
- PARALLEL
- Sponsor Type
- OTHER
- Responsible Party
- SPONSOR INVESTIGATOR
- PI Title
- PhD-student
Study Record Dates
First Submitted
September 2, 2022
First Posted
September 14, 2022
Study Start
June 29, 2022
Primary Completion
April 30, 2024
Study Completion
September 30, 2025
Last Updated
September 23, 2024
Record last verified: 2024-09