Excessive Daytime Sleepiness Predicts Neurodegeneration in Idiopathic REM Sleep Behavior Disorder

Interesting to see how excessive daytime somnolence (sleepiness) predicts which patients with RBD go on to get PD... and strange that it does not predict all neurodegenerative outcomes. I would have thought excessive daytime somnolence was influenced by many factors, but perhaps this suggest specific pathological involvement of a brain structure related to PD (the locus ceruleus?)

Sleep. 2017 Mar 16. doi: 10.1093/sleep/zsx041. [Epub ahead of print]
Zhou J, Zhang J, Lam SP, Chan JW, Mok V, Chan A, Li SX, Liu Y, Tang X, Yung WH, Wing YK.

https://academic.oup.com/sleep/article-abstract/doi/10.1093/sleep/zsx041/3072757/Excessive-Daytime-Sleepiness-Predicts?redirectedFrom=fulltext

STUDY OBJECTIVES: To determine the association of excessive daytime sleepiness (EDS) with the conversion of neurodegenerative diseases in patients with idiopathic REM sleep behavior disorder (iRBD).

METHODS: A total of 179 patients with iRBD (79.1% males, mean age = 66.3 ± 9.8 years) were consecutively recruited. Forty-five patients with Epworth Sleepiness Scale score ≥ 14 were defined as having EDS. Demographic, clinical and polysomnographic data were compared between iRBD patients with and without EDS. The risk of developing neurodegenerative diseases was examined using Cox proportional hazards model.

RESULTS: After a mean follow-up of 5.8 years (SD = 4.3 years), 50 patients (27.9%) developed neurodegenerative diseases. There was a significantly higher proportion of conversion in patients with EDS compared with those without EDS (42.2 % vs 23.1%, P = 0.01). EDS significantly predicted an increased risk of developing neurodegenerative diseases (adjusted hazard ratios [HR] = 2.56, 95% confidence interval [CI] 1.37-4.77) after adjusting for age, sex, body mass index, current depression, obstructive sleep apnea, and periodic limb movement during sleep. Further analyses demonstrated that EDS predicted the conversion of Parkinson's disease (PD) (adjusted HR = 3.55, 95% CI 1.59-7.89), but not dementia (adjusted HR = 1.48, 95% CI 0.44-4.97).

CONCLUSIONS: EDS is associated with an increased risk of developing neurodegenerative diseases, especially PD, in patients with iRBD. Our findings suggest that EDS is a potential clinical biomarker of α-synucleinopathies in iRBD.