Prevalence of Rapid Eye Movement-related Obstructive Sleep Apnea in Adult Narcolepsy

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 AHI(REM)/AHI(NREM) ≥2 and AHI(NREM) <15; and Definition #3, an overall AHI ≥5 and AHI(REM)/AHI(NREM) ≥2 and AHI(NREM) <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.