Does Olfactory Training Improve Olfaction in a Population With Normal Sense of Smell?

St. Olavs Hospital

Status: Completed

Conditions: People With Normal Sense of Smell

Treatments: Behavioral: ordinary olfactory training; Behavioral: intensive olfactory training

Study type: Interventional

Funder types: Other

Identifiers

NCT02980718

2016/837

Details and patient eligibility

About

Awareness of the sense of smell in the western population has been low. Most people do not think about the consequences of absence of smell (anosmia). Reduction in sense of smell (hyposmia) can influence everyday life. In situations of stress anosmia can be life threatening for example when there is a fire. Cooks may lose their job. Not being able to enjoy food and drink interferes with quality of life. The causes of olfactory dysfunction (OD) vary. Most often OD is associated with upper respiratory tract infections, disease of the nose and sinuses or head injuries. OD may be congenital, age related or associated with neurological disorders. Hyposmia occurs in up to 85% of cases of Parkinson's and may be the first symptom of both Parkinson's and Alzheimer's disease several years before the mental changes occur.

Knowledge and focus on OD has until recently been low among most physicians and treatment options have often not been available. Different approaches to improve OD have been tried with variable effect depending on the cause of OD. There are studies on corticosteroids, zinc gluconate and vitamin A. In recent years, olfactory training has been launched as a promising treatment option. Most studies with olfactory training are done with patients with OD. A recently published review describes 10 studies with olfactory training among 639 patients and concludes that daily stimulation with odorants (odor concentrate) over a limited period time is a promising treatment. The suggested duration of olfactory training varies from 3 to 14 months. Different intensities of olfactory training were compared in patients with post-viral OD. Olfaction was more improved by the high concentration of odorant than by the low concentration.

A small number of studies have shown that the olfactory nerve to some extent can be trained in persons with normal sense of smell, but we need more experience and structured studies to be able to conclude with greater certainty about the effect of olfactory training in this population.

This study examines whether intensive olfactory training improves the sense of smell more than ordinary olfactory training in subjects with normal olfaction (normosmia) and examines self-evaluation of olfactory function.

Full description

Sub-study: Part of the participants (45/200) will be included in a pilot study which will be an analytical observational study to compare olfactory bulb volume measured on MRI three times during a year, while at the same time resting state fMRI will be measured before and after olfactory training. There is not sufficient data in the literature for power calculations and this sub-study is therefore a pilot study.

Enrollment: 200 patients

Sex: All

Ages: 18 to 65 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• TDI score > 30.5 measured by Sniffin'Sticks

Exclusion criteria

• Not able to follow the olfactory training or follow-up (language, practical implementation, mental condition)
• Disease affecting olfaction (sinusitis, pronounced allergies, recent nasal surgery, Alzheimer's, Parkinson, MS, COPD)

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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200 participants in 3 patient groups

intensive olfactory training

Experimental group

Description:

90 participants will undergo intensive olfactory training. They will sniff on four selected odors (10 seconds on each odor bottle in a total of 4 minutes) every morning and evening for 3 months and they will be instructed in the principles of the logbook for olfactory training.

Treatment:

Behavioral: intensive olfactory training

ordinary olfactory training

Experimental group

Description:

90 participants will undergo ordinary olfactory training. They will sniff on four selected odors (10 seconds on each odor bottle in a total of 40 seconds) every morning and evening for 3 months and they will be instructed in the principles of the logbook for olfactory training.

Treatment:

Behavioral: ordinary olfactory training

controls

No Intervention group

Description:

20 participants represent a control group with no olfactory training