Inaccurate self-report of olfactory dysfunction in REM Sleep Behaviour Disorder and implications for prognosis

Amber Roguski*, Michal Rolinski, Matt W Jones, Alan Whone

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

Abstract

Introduction

The earliest stages of alpha-synucleinopathies are accompanied by non-specific prodromal symptoms such as diminished sense of smell, constipation and depression, as well as more specific prodromal conditions including REM Sleep Behaviour Disorder (RBD). While the majority of RBD patients will develop an alpha-synucleinopathy, one of the greatest clinical challenges is determining whether and when individual patients will phenoconvert. Clinical evaluation of a patient presenting with RBD should therefore include robust and objective assessments of known alpha-synucleinopathy prodromes.

Methods

This study compared olfactory function self-report measures with psychophysical ‘Sniffin’ Stick 16-item Identification’ test scores in Control (n = 19), RBD (n = 16) and PD (n = 17) participants.

Results

We confirm that olfactory test scores are significantly diminished in RBD and PD groups compared to Controls (p < 0.001, One-Way ANOVA with Tukey-Kramer Post-Hoc, effect size = 0.401). However, RBD participants were only 56 % accurate when self-reporting olfactory dysfunction, hence markedly less likely to perceive or acknowledge their own hyposmia compared to Controls (p = 0.045, Fisher’s Exact Test, effect-size = 0.35).

Conclusion

When isolated RBD presents with hyposmia, there is an increased likelihood of phenoconversion to Parkinson’s Disease (PD) or Dementia with Lewy Bodies (DLB); unawareness of olfactory dysfunction in an individual with isolated RBD may therefore confound differential diagnosis and prognosis. Our results evidence the fallibility of olfactory function self-report in the context of RBD prognosis, indicating that clinical assessments of RBD patients should include more reliable measures of olfactory status.

Original languageEnglish
Article number100176
JournalClinical Parkinsonism & Related Disorders
Volume8
Early online date17 Dec 2022
DOIs
Publication statusPublished - 1 Jan 2023

Bibliographical note

Funding Information:
AR was supported by a UKRI/BBSRC CASE PhD studentship in partnership with Eli Lilly & Company [grant number BB/S507295/1].

Funding Information:
AW is salaried by the University of Bristol. In the past 12 months AW has received speaker fee honorariums from Novo Nordisk and has advised Vivifi Biotech for a total of 10 h. AW has received research grants from North Bristol Trust Charities; University of Bristol Alumni Scobie Award; Cure Parkinson’s Trust; EPSRC; Wellcome Trust; Academy of Medical Sciences; Elizabeth Blackwell Institute for Health Research; David Telling Trust; NIHR. There is no conflict of interest.

Publisher Copyright:
© 2022

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