Objective: To determine the contribution of cognitive impairment to color discrimination deficits in idiopathic REM sleep behavior disorder (iRBD). Background iRBD is a parasomnia considered as a risk factor for Parkinson9s disease or dementia with Lewy bodies. Markers of neurodegeneration have been dentified in iRBD, such as cognitive impairment. Color discrimination deficit has also been reported in iRBD using the Farnsworth-Munsell 100 hue test (FM-100). However, the pathophysiology of this dysfunction remains poorly understood (retinal structure changes versus contribution of cognitive impairment). Design/Methods: Thirty-five iRBD patients with mild cognitive impairment (MCI; 26 men; mean age, 70.60 ± 6.99), 22 iRBD patients without cognitive impairment (15 men; mean age, 66.05 ± 6.92) and 20 healthy controls (15 men; mean age, 69.45 ± 8.56) performed the FM-100 combined with a comprehensive neuropsychological evaluation. MCI diagnosis was based on standard criteria. One-way analysis of covariance, with age taken as a covariant since it affects FM-100 performances in a normal population, was done to compare the three groups using the square root of the total error score (√TES). Pearson9s Chi-square test was used for comparing the proportion of individuals in each group showing significant abnormal scores. Results: The three groups did not differ for age and gender. iRBD patients with MCI (mean √TES, 13.41 ± 2.31) performed poorly on the FM-100 compared to iRBD patients without cognitive impairment (mean √TES, 11.52 ± 2.77) and controls (mean √TES, 10.50 ± 2.31; p= 0.001). iRBD patients with MCI had a higher proportion of individuals with significant abnormal scores (20/35 or 57%) than iRBD patients without cognitive impairment (7/22 or 32%) and controls (5/20 or 25%; p = 0.037). iRBD patients without cognitive impairment were comparable to controls on both measures. Conclusions: We found a major contribution of cognitive impairment to color discrimination deficits reported in iRBD. Supported by: Canadian Institutes of Health Research (CIHR) and Fonds de la Recherche en Sante du Quebec (FRSQ). Disclosure: Dr. Bertrand has nothing to disclose. Dr. Postuma has nothing to disclose. Dr. Genier-Marchand has nothing to disclose. Dr. Montplaisir has received personal compensation for activities with Boehringer Ingelheim, Servier, and Shire. Dr. Montplaisir has received research support form Sanofi Synthelabo and GlaxoSmithKline. Dr. Gagnon has nothing to disclose.
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