Objective The association between narcolepsy and rapid eye movement (REM)-related obstructive sleep apnea (OSA) has not been reported. This study aimed to examine the prevalence of REM-related OSA in narcolepsy patients. Methods From January 2013 to April 2018, 141 adult patients were diagnosed with narcolepsy using nocturnal polysomnography and the multiple sleep latency test. The prevalence of REM-related OSA in narcolepsy patients was retrospectively reviewed. Three criteria were used to determine REM-related OSA: Definition #1, an overall apnea-hypopnea index (AHI) ≥5 and AHI during REM (AHIREM)/AHI during non-rapid eye movement (NREM) (AHINREM) ≥2; Definition #2, an overall AHI ≥5 and AHIREM/AHINREM≥2 and AHINREM <15; and Definition #3, an overall AHI ≥5 and AHIREM/AHINREM≥2 and AHINREM <8 plus an REM sleep duration >10.5 minutes. Results Of the 141 narcolepsy patients, 26 were diagnosed with narcolepsy with cataplexy (NA-CA) and 115 with narcolepsy without cataplexy (NA w/o CA). Seventeen patients with NA-CA and 39 with NA w/o CA had OSA. According to Definition #1, the prevalence of REM-related OSA was 47.1% and 41.0%, respectively, in OSA patients with NA-CA and NA w/o CA; according to Definition #2, the respective prevalence was 47.1% and 38.5%, while that according to Definition #3 was 41.2% and 25.6%. No significant differences were found in the prevalence of REM-related OSA for each definition. Conclusion A high prevalence of REM-related OSA was confirmed in adult narcolepsy patients with OSA. Compared to previous reports, we noted a high frequency of REM-related OSA satisfying the relatively strict Definition #3. These results might reflect the pathophysiological characteristics of narcolepsy.
Keywords: REM-related obstructive sleep apnea; narcolepsy; obstructive sleep apnea.