Hummel, T., Rissom, K., Reden, J., Hähner, A. Weidenbecher, M.,Hüttenbrink, K. (2009) Effects of Olfactory Training in Patients with Olfactory Loss. Laryngoscope, Volume 119, Issue 3, March 2009, pages 496-499

University of California, Berkeley

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

Effects of Olfactory Training in Patients with Olfactory Loss

A meta-analysis was performed based on the discovery of olfactory training improving the olfactory ability. The samples include health elders and the patients of Parkinson disease, olfactory diseases, postinfectious olfactory loss, and posttraumatic olfactory loss. The result shows a positive and statistically significant effect of olfactory training in the case of all olfactory abilities. Interestingly, a difference was observed between effectiveness of olfactory training for threshold and other evaluated criteria. A reasonable explanation is that identification and discrimination are dependent on individuals' cognitive abilities, while threshold is more related to peripheral olfactory system. 

Further research on the effect of olfactory training

In order to investigate the effects of olfactory training vary by duration, the same testing method was performed over a period of 6 years. In total 111 patients were included on this experiment. The result shows that the recovery of olfactory function improved dramatically in the first 16 weeks, after that period, the patients began to recover in a slower pace. Overall, the olfactory training can improve the patients' olfactory functions continuously over a long period.

Long term olfactory training

An olfactory training using "Sniffin' Sticks" was performed on 91 patients aged between 50 to 84 years. The whole speculation lasted for five months. The result indicated that around 30% of the patient score a higher TDI-score after the training. The result is consistent with the experiment performed on patients of all ages. Therefore, the effect of aging on olfactory training can be neglected. Moreover, this experiment also recorded the score of auditory function. However, it did not show any significant difference between the performance before and after the training.

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