Does Olfactory Training Improve Olfaction in a Population With Normal Sense of Smell?
Condition: People With Normal Sense of Smell
Study type: Interventional

Summary: 
      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.
    

Detailed 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.
    

Intervention name(s): intensive olfactory training; ordinary olfactory training
Intervention type(s): Behavioral; Behavioral
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Olfaction training; Smell