Jiramongkolchai, P., Jones, M., Peterson, A. (2021). Association of Olfactory Training With Neural Connectivity in Adults With Postviral Olfactory Dysfunction. JAMA Otolaryngol Head Neck Surg, Volume 147, Issue 6, pages 502-509. https://doi.org/10.1001/jamaoto.2021.0086

Association of Olfactory Training With Neural Connectivity in Adults With Postviral Olfactory Dysfunction

COVID-19 patients often report experiencing parosmia, even after the other symptoms had already recovered. However, through olfactory training, the patients' olfactory functions recovered slowly. The olfactory system in the patients exhibited significant plasticity and the ability to develop new neural connections.

University of California, Berkeley

Olfactory training is a non-pharmacological and non-surgical treatment for patients with olfactory dysfunction. UPSIT (University of Pennsylvania Smell Identification Test) is the most common olfactory training in North America. UPSIT is based on microencapsulated odorants released from the surface of strips. Each subject tags 40 odorants on a multiple-choice list.

Olfactory training

Kronenbuerger, M. & Pilgramm, M. (2020). Olfactory Training. Treasure Island: StatPearls Publishing.

Olfactory Training (2020)

Hummel, T., Sekinger, B., Wolf, S., Pauli, E., & Kobal, G. (1997). 'Sniffin' Sticks': Olfactory Performance Assessed by the Combined Testing of Odor Identification, Odor Discrimination and Olfactory Threshold. Chemical Senses, Volume 22, Issue 1, February 1997, Pages 39-52, https://doi.org/10.1093/chemse/22.1.39

'Sniffin' Sticks': Olfactory Performance Assessed by the Combined Testing of Odor Identification, Odor Discrimination and Olfactory Threshold (1997)

Olfactory training was performed by 40 subjects, and other 16 patients in the group did not perform the training. The postinfectious group (URTI) consisted of 35 patients; the post-traumatic group of 7 patients; the idiopathic group of 14 patients. The training tested on the abilities of threshold, discrimination, and identification, the overall score was reported as TDI-score. The study reported that the approximately 30% of patients increased their olfactory function over a period of 12 weeks, and the improvement was found in all three groups of patients. However, more research still need to be done for determining the duration of the improvement, responsiveness to odors at the level of the olfactory epithelium, volume of the olfactory bulb, and effects using different testing methods.

Medical effects of olfactory training on patients

In an empirical study of older adults (mean age around 80 years), three months of olfactory training led to significantly higher scores in odor threshold and odor identification performance compared to a control group. However, olfactory scores did not significantly increase from pre-test to post-test within the training group itself. This indicates that olfactory training in older adults prevents age-related olfactory deterioration rather than active improvement of olfactory function (Schriever et al., 2014).

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