Olfactory Training in Patients with Parkinson's Disease

Antje Haehner,Alexander Storch,Thomas Hummel,Clara Tosch,Lisa Klingelhoefer,Martin Wolz,Mareike Fauser,Heinz Reichmann,Hiroaki Matsunami

doi:10.1371/journal.pone.0061680

Abstract

ObjectiveDecrease of olfactory function in Parkinson's disease (PD) is a well-investigated fact. Studies indicate that pharmacological treatment of PD fails to restore olfactory function in PD patients. The aim of this investigation was whether patients with PD would benefit from “training” with odors in terms of an improvement of their general olfactory function. It has been hypothesized that olfactory training should produce both an improved sensitivity towards the odors used in the training process and an overall increase of olfactory function.MethodsWe recruited 70 subjects with PD and olfactory loss into this single-center, prospective, controlled non-blinded study. Thirty-five patients were assigned to the olfactory training group and 35 subjects to the control group (no training). Olfactory training was performed over a period of 12 weeks while patients exposed themselves twice daily to four odors (phenyl ethyl alcohol: rose, eucalyptol: eucalyptus, citronellal: lemon, and eugenol: cloves). Olfactory testing was performed before and after training using the “Sniffin' Sticks” (thresholds for phenyl ethyl alcohol, tests for odor discrimination, and odor identification) in addition to threshold tests for the odors used in the training process.ResultsCompared to baseline, trained PD patients experienced a significant increase in their olfactory function, which was observed for the Sniffin' Sticks test score and for thresholds for the odors used in the training process. Olfactory function was unchanged in PD patients who did not perform olfactory training.ConclusionThe present results indicate that olfactory training may increase olfactory sensitivity in PD patients.

Highlights

Impairment of olfaction is a characteristic and early feature of Parkinson’s disease (PD)
Compared to baseline, trained PD patients experienced a significant increase in their olfactory function, which was observed for the Sniffin’ Sticks test score and for thresholds for the odors used in the training process
Olfactory function was unchanged in PD patients who did not perform olfactory training

Summary

Introduction

Impairment of olfaction is a characteristic and early feature of Parkinson’s disease (PD). Recent data indicate that .95% of patients with PD present with significant loss of olfactory function [1] whose impact on daily life is often underappreciated [2]. The sense of smell makes a significant contribution to the quality of life and the ability to experience pleasure. According to a study by Politis et al [3] olfactory loss belongs to the top-five most prevalent motor and non-motor symptoms in early stage PD patients that affect their quality of life. Pain is referred to as a more prevalent troublesome non-motor problem in this patient group. Patients with impaired olfaction are more likely to experience depressive symptoms as they express severe limitations in relation to the enjoyment of food and drinks and socializing [4], [5]

Methods

Results

Conclusion