Cognitive decline in association with hyposmia in idiopathic rapid eye movement sleep behavior disorder: a prospective 2‐year follow‐up study

Abstract

Background and purpose The aim was to analyze the characteristics and progression of cognitive dysfunction in non‐demented idiopathic rapid eye movement sleep behavior disorder (iRBD) patients with baseline olfactory function. Methods From a prospective polysomnography‐confirmed iRBD cohort, 25 patients (16 patients in 2‐year follow‐up) and 13 normal controls were included. Initial and 2‐year follow‐up cognitive functions were analyzed with olfactory function and 18F‐fluorinated‐N‐3‐fluoropropyl‐2β‐carboxymethoxy‐3β‐(4‐iodophenyl)‐nortropane (18F‐FP‐CIT) uptake in deep nuclei initially. Results Idiopathic RBD patients had impaired attention, memory and executive function compared to controls. Baseline cognitive tests were comparable between the iRBD subgroups with and without hyposmia. 18F‐FP‐CIT uptake tended to be lower in the hyposmic group than in the normosmic group. The olfactory test score was positively correlated with amygdala uptake in iRBD patients (P = 0.027). After 2 years, visuospatial and verbal memory dysfunction worsened more in hyposmics than in normosmics. Lower initial olfactory test score was associated with more severe declines in verbal memory function. Conclusions Hyposmia may be a predictive sign of cognitive decline in iRBD patients.

Brainstem Quadruple Aberrant Hyperphosphorylated Tau, Beta-Amyloid, Alpha-Synuclein and TDP-43 Pathology, Stress and Sleep Behavior Disorders

“…Clinical signs and cognition deficits are very useful to detect in early stages of neurodegeneration. McDade et al [ 49 ] described RBD as associated with gait changes, while Shin et al [ 50 ] made the association between RBD, cognitive decline and hyposmia.…”

Biomarkers of conversion to α-synucleinopathy in isolated rapid-eye-movement sleep behaviour disorder

“…33 In one study, hyposmia was closely correlated with progressive decline in visuospatial function and verbal memory in patients with isolated RBD followed over 2 years, suggesting that hyposmia might also predict future conversion to dementia with Lewy bodies. 34 Although hyposmia also correlates strongly with the presence of phosphorylated α-synuclein aggregates on skin biopsy, 35 it cannot distinguish…”

Neuropsychological evaluation of phenoconversion risk in REM sleep behaviour disorder: A scoping review

“…Following elimination of 1498 duplicates, 1034 citations were potentially relevant and therefore screened by title and abstract: 495 were excluded on the basis of the selection/exclusion criteria, while 539 were reviewed by a multidisciplinary team, who, using an abstract‐based selection process, selected 263 full‐text articles for data evaluation. Of these, 20 were finally included in our review (Alotaibi et al, 2019; Arnaldi et al, 2021, 2022; Campabadal et al, 2020; Fantini et al, 2011; Iranzo et al, 2006, 2013; Marchand et al, 2017, 2018; Postuma et al, 2009; Roascio et al, 2022; Sakurai et al, 2014; C. Shin et al, 2019; J. H. Shin et al, 2021; Sumi et al, 2022; Terzaghi et al, 2013, 2019; Yoo et al, 2021; Yoon et al, 2022; Youn et al, 2016).…”

“…In 6 of the 20 studies analysed, the neuropsychological tests performed were not grouped into cognitive domains (Alotaibi et al, 2019;Sakurai et al, 2014;C. Shin et al, 2019;J.…”

“…South Korea [C. Shin et al, 2019;J. H. Shin et al, 2021;Yoo et al, 2021;Yoon et al, 2022;Youn et al, 2016]).…”