Abstract
Aim: Rapid eye movement (REM) sleep behaviour disorder (RBD) is a sleep abnormality heralded by the absence of physiological atonia in REM sleep and dream enactment behaviour. Idiopathic RBD (iRBD), dia g nosed when no primary RBD cause can be identified, is a marker of prodromal synucleinopathy with a high conversion rate to overt neurodegenerative disorders from the synucleinopathy group.
The aim of this cross-sectional study was to investigate olfactory function in iRBD patients and its relation to other symptoms. Patients and methods: This study included 54 iRBD patients with a median age of 67 (IQR 63-72) years; the 37 control subjects, matched by gender and age, had a median age of 67 (57.5-70.0) years.
All subjects underwent a complex examination, which included olfactory testing using the University of Pennsylvania Smell Identifi cation Test (UPSIT). Results: In total, 62.9% of iRBD patients had either total loss of olfactory function or severe hyposmia.
In contrast, only 8.1% of controls showed such a degree of olfactory dysfunction. Furthermore, we found that the percentage of REM sleep without atonia on polysomnography negatively correlates with the UPSIT score (P < 0.01).
Conclusion: This study demonstrated a signifi cantly lower olfactory function in the iRBD group compared to controls.