The combined effect of REM sleep behavior disorder and hyposmia on cognition and motor phenotype in Parkinson's disease

Further evidence that RBD and hyposmia are probably indicative of more severe form of PD with greater akinetic-rigidity and cognitive impairment... I think this is already known, but it is nice to see concordant results in other settings. This likely has implications about the burden and distribution of PD pathology....

J Neurol Sci. 2016 Sep 15;368:374-8. doi: 10.1016/j.jns.2016.07.057. Epub 2016 Jul 26.

Kang SH, Lee HM, Seo WK, Kim JH, Koh SB.

http://www.jns-journal.com/article/S0022-510X(16)30470-1/abstract

BACKGROUND:

Olfactory dysfunction and REM sleep behavior disorder (RBD) are recognized as pre-motor symptoms of Parkinson's disease (PD). Cognitive dysfunction is observed at a high rate even in the early stages of PD as an important non-motor symptom. PD has been classified in different subtypes and it is unknown if olfactory dysfunction and RBD occur more often in one particular subtype. We investigated the relationship between olfactory impairment, RBD, initial cognitive performance and motor phenotype in PD.

METHOD:

Nighty-eight patients with drug-naïve idiopathic PD who visited the Movement Disorders Unit of Korea University Guro Hospital, Seoul, Korea from March 2012 to February 2014 were retrospectively included. Patients were divided into tremor-dominant-type and akinetic-rigid-type PD subgroups using part III of the Unified Parkinson's Disease Rating Scale. Olfaction was assessed by the Cross Cultural Smell Identification Test. RBD was screened using screening questionnaires. Initial cognitive function was assessed with Mini-Mental State Examination.

RESULT:

The PD-normosmia group had higher MMSE scores (p=0.008). PD patients who have both RBD and olfactory dysfunction had lower MMSE scores (p=0.013). Presence of both RBD and hyposmia in PD patients was more strongly correlated with poor cognitive dysfunction. PD patients with RBD and/or hyposmia primarily exhibited the akinetic-rigidity phenotype.

CONCLUSION:

Olfactory dysfunction and RBD differed according to the motor phenotypes of PD. This suggests that olfactory dysfunction and RBD might relate to prognosis in patients with PD. Patients who have both hyposmia and RBD were more likely to exhibit cognitive dysfunction.

Copyright © 2016 Elsevier B.V. All rights reserved.