Comorbid OSA and RBD: the evil or the friend?

<bold>Introduction:</bold> Comorbid obstructive sleep apnea (OSA) and rapid eye movement (REM) sleep behavior disorder (RBD) are highly common, with 34%–61% of RBD patients (pts) exhibiting OSA. The influence of muscle atonia during REM sleep on OSA severity and sleep architecture is still controversial. <bold>Aims:</bold> To compare clinical and polysomnographic characteristics between OSA with isolated RBD (OSA-RBDi) and OSA without RBD (OSA-non-RBD) pts. <bold>Methods:</bold> A cross-sectional analysis was made comparing pts with OSA-RBDi followed in a sleep center with 29 OSA-non-RBD controls matched for age, respiratory distress index (RDI) and sex. Pts taking antidepressants/benzodiazepine or with previous respiratory, sleep or neurodegenerative diseases were excluded. Analyzes were performed in SPSS-Statistics v.27.0 with statistical significance set at 0.05. <bold>Results:</bold> A total of 22 OSA-RBDi pts were included, mostly men (n=14) with 70.3 ± 9,2 years, an average body mass index of 29,8 kg/m2 and mean RDI of 19.5/h. OSA-RBDi pts presented with more onset insomnia (p=0,05), lower sleep efficiency (p=0,001; duo to higher WASO (p=0,004)) and lower RDI during REM sleep (p=0,03) and oxygen desaturation index (p=0,01) than OSA-non-RBD. There were no significant demographic differences between groups or in the remaining parameters evaluated, even when analyzed for OSA severity subgroups. <bold>Conclusions:</bold> Comorbid OSA and RBD seem to be associated with lower sleep efficiency and increased onset insomnia, which should alert us to the suspicion of this diagnosis. On the other hand, the prevalence of REM-related RDI and oxygen desaturation was lower in OSA-RBDi, possible reflecting a protective role of RBD on OSA. We identified sample size as the main limitation of our study.