Effects of olfactory training: a meta-analysis

Abstract

The neural plasticity of the olfactory system o ers possibilities of treatment in terms of stimulation of the sense of smell, and different studies have suggested e ectiveness of smell training, i.e., daily exposition to certain odors. To obtain reliable and precise estimates of overall treatment bene t on the olfactory function, we meta-analyzed the e ects of smell training reported in 13 previous studies. We analyzed the smell training e ectiveness across three di erent olfactory abilities-smell identi cation, discrimination and threshold for odor detection. We found a signi cant, positive e ect of olfactory training for all olfactory abilities, with large e ects of training on identi cation, discrimination and TDI-score and small-to-moderate e ect in the case of threshold for odor detection. Interestingly, the pattern of results di ered across Sni n' Sticks subtests depending on the origin of participants' smell disorder, and the smell training duration in uenced its e ectiveness in the case of identi cation and the TDI score. Although the exact mechanism of olfactory recovery following the smell training still requires further investigation, our meta-analysis showed that such training should be considered an addition or alternative to existing smell treatment methods.

Olfactory Training in Post-COVID-19 Persistent Olfactory Disorders: Value Normalization for Threshold but Not Identification

“…T-recovery could be explained by a peripheral regenerative [ 43 ] effect of OT with a regrowth of olfactory neurons, increase in olfactory receptor expression or a higher specific affinity for those existing as Hummel et al [ 44 ] explained observing an improvement of electro-olfactogram after OT; and I-recovery (with D-recovery) by a more central processing allowing an olfaction dedicated area connectivity reorganization [ 24 , 45 ] and increase in olfactory bulbs [ 46 ]. More recently, Sorokowska et al [ 25 ] reported, in a meta-analysis (n > 879), a large and significant post-OT increase both on D and I. However, they [ 25 ] also mentioned a small to moderate effect on T, which is in contradiction with our results despite that we used the same PEA threshold in both visits.…”

“…This involved a 6-month olfactory training with daily odor exposure, twice a day (two sessions) with two different random odors from the kit in the morning and the evening (four different odors per day). We decided to run the olfactory training for 6 months as it was described [ 25 ] to be more effective than the 12 week previously described protocol [ 17 ], especially since odors are renewed every 3 months [ 15 ].…”

The olfactory bulb - gateway for SARS-Cov-2?

“…Although we still cannot efficiently cure anosmia, neural plasticity of the olfactory system offers treatment options in terms of stimulating the sense of smell. In her article, Sorokowska states that the regenerative capabilities of olfactory pathways vary from changes in membrane excitability, changes in synaptic efficiency to neurogenesis and apoptosis [27]. Studies which dealt with this "olfactory training", show promising results.…”

Riech- und Schmeckstörungen

“…Empfohlen wird die Durchführung des Riechtrainings über einen Zeitraum von 6–9 Monaten. Je schneller das Riechtraining nach einer Riechstörung aufgenommen wird, desto besser erscheinen die Ergebnisse [ 52 ].…”

“…Das Riechtraining verbessert so v. a. bei postinfektiöser, aber auch zu geringerem Anteil bei posttraumatischer und idiopathischer Riechstörung signifikant die Riechwahrnehmung [ 1 , 52 , 53 ].…”