Adherence and Efficacy of Olfactory Training as a Treatment for Persistent Olfactory Loss

Abstract

Background Among emerging therapies, olfactory training (OT) has been proposed as a potential treatment for persistent olfactory loss. This treatment has been suggested to improve olfactory function via sensorineural modulation from repeated odor exposure. However, due to the long treatment period that is required, many patients discontinue the treatment or do not follow the treatment regimen appropriately, potentially biasing estimates of treatment success. Moreover, spontaneous improvement is known to occur without any interventions. Objectives We evaluated both the adherence rates and the efficacy of OT in patients with persistent postinfectious, posttraumatic, or idiopathic olfactory loss. Methods Prospective observational study. Twenty-five patients with persistent olfactory loss underwent OT. Protocol adherence and olfactory function (scores on the University of Pennsylvania Smell Identification Test or UPSIT) were assessed 3 and 6 months after the initiation of treatment. A minimum improvement of 5 UPSIT points was considered clinically significant and adherence throughout the study. Results The adherence rate of the patients after 3 months was 88% and after 6 months was 56%. The corresponding percentages of clinical improvement were 23.5% and 25%. There was no relation of age, sex, time of olfactory loss, race, the degree of olfactory loss, etiology, education, and type of training to the adherence rate or treatment efficacy. Conclusions In this patient population, adherence to training remained high in the first 3 months of OT but declined moderately thereafter. The observed prevalence and degree of improvement were similar to that reported a number of studies, including some studies whose patients did not receive OT.