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| ID | Type | Description | Link |
|---|---|---|---|
| 2021-06527 | Other Grant/Funding Number | Swedish Research Council |
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Hyposmia, a reduced sense of smell, is commonly linked to viral infections like COVID-19. Currently, the sole recommended treatment is olfactory training, a method that is both time-intensive and limited in its effectiveness. Our team has previously evaluated a new type of olfactory training using nasal inserts that show increased adherence to training (compared to standard olfactory training using common household odors) but with similar treatment effect. The investigators recently demonstrated that brief transcutaneous vagus nerve stimulation (VNS) in the cymba conchae region affected participants olfactory abilities but only when a stimulation frequency relevant to olfactory bulb processing frequencies was used. The notion that VNS might modulate olfactory functions stems from findings in rats where VNS of the cervical nerve inhibited neurons within the periglomerular layers of the olfactory bulb. Although there is no known monosynaptic connection between the vagus nerve and the olfactory system in humans, VNS activates areas with mono-synaptic connections to the olfactory bulb, such as amygdala, hippocampus, and the hypothalamus. Given that VNS modulates the olfactory bulb in rats and our treatment protocol modulate olfactory functions in humans, the investigators hypothesize that VNS, when paired with olfactory training, will enhance olfactory functions in patients with hyposmia.
Participants with hyposmia will be recruited and randomly assigned to one of two treatment groups. One group will engage in olfactory training using nasal inserts while the other will use olfactory training with nasal inserts along with VNS. Both interventions will take place at home, Monday through Friday, over a two-month period. To evaluate the outcomes, subjective and objective measures of olfactory function will be collected before, during, and after the treatment, along with assessments of quality of life and overall well-being. Treatment adherence will also be evaluated at the end of treatment.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Olfactory training with nasal inserts + VNS | Experimental | Participants will complete olfactory training with scented nose plugs along with VNS |
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| Olfactory training with nasal inserts only | Active Comparator | Participants will complete olfactory training with scented nose plugs |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Nasal Insert + VNS | Other | Participants will complete olfactory training with scented nose plugs along with VNS |
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| Measure | Description | Time Frame |
|---|---|---|
| Sniffin' Sticks TDI test (objective olfactory function) | Objective olfactory function will be measured using the Sniffin' Sticks TDI extended test (Burghart Messtechnik) which gives separate scores for odor threshold, odor discrimination, and odor identification; as well as a summated score (TDI) of objective olfactory function. | From enrollment to the end of treatment at 8 weeks |
| Self rated olfaction questionnaire (subjective olfactory function) | Does the use of VNS increase the effect of olfactory training on subjective qualitative (parosmia) and quantitative (hyposmia) symptoms compared to only olfactory training? For this outcome, we will use self-ratings of qualitative and quantitative olfactory function, for example "Do you experience smell distortion (parosmia)?" (if yes, rate your problem from 0 to 10) and "rate your sense of smell from 0 to 10" | From enrollment to the end of treatment at 8 weeks |
| General Wellbeing Questionnaire (general wellbeing) | Does the use of VNS increase the effect of olfactory training on subjective general wellbeing compared to only olfactory training? For this outcome, we will use the General Wellbeing Questionnaire (GWB). | From enrollment to the end of treatment at 8 weeks |
| Adherence to training questionnaire (Compliance) | Does the use of VNS affect the compliance of olfactory training compared to olfactory training only? For this outcome, we will use a questionnaire that participants answer during their final visit. The questionnaire separately assesses consistency, perceived tediousness, forgetfulness, and cause for potential discontinuation of the training, for example by asking "how many times did you forget your training?" | From enrollment to the end of treatment at 8 weeks |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Karolinska Institutet | Solna | Stockholm County | 17165 | Sweden |
anonymized data
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| ID | Term |
|---|---|
| D000086582 | Anosmia |
| D000857 | Olfaction Disorders |
| D012678 | Sensation Disorders |
| ID | Term |
|---|---|
| D009461 | Neurologic Manifestations |
| D009422 | Nervous System Diseases |
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
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| Nasal Insert | Other | Participants will complete olfactory training with scented nose plugs |
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