• Sleep Medicine and Psychophysiology
• /
• v.24 no.2
• /
• pp.106-117
• /
• 2017

Objectives: Obstructive sleep apnea (OSA) is a sleep-related breathing disorder that is characterized by repetitive collapse or partial collapse of the upper airway during sleep in spite of ongoing effort to breathe. It is believed that OSA is usually worsened in REM sleep, because muscle tone is suppressed during REM sleep. However, many cases showed a higher apnea-hypopnea index (AHI) during NREM sleep than during REM sleep. We aimed here to determine the characteristics of REM sleep-dependent OSA (REM-OSA) and NREM sleep-dependent OSA (NREM-OSA). Methods: Five hundred sixty polysomnographically confirmed adult OSA subjects were studied retrospectively. All patients were classified into 3 groups based on the ratio between REM-AHI and NREM-AHI. REM-OSA was defined as REM-AHI/NREM-AHI > 2, NREM-OSA as NREM-AHI/REM-AHI > 2, and the rest as sleep stage-independent OSA (IND-OSA). In addition to polysomnography, questionnaires related to subjective sleep quality, daytime sleepiness, and emotion were completed. Chi-square test, ANOVA, and ANCOVA were performed. Results: There was no age difference among subgroups. The REM-OSA group was comprised of large proportions of mild OSA and female OSA patients. These patients experienced poor sleep and more negative emotions than other two groups. The AHI and oxygen desaturation index (ODI) were lowest in REM-OSA. Sleep efficiency and N3 percentage of REM-OSA were higher than in NREM-OSA. The percentage of patients who slept in a supine position was higher in REM-OSA than other subgroups. IND-OSA showed higher BMI and larger neck circumference and abdominal circumference than REM-OSA. The patients with IND-OSA experienced more sleepiness than the other groups. AHI and ODI were highest in IND-OSA. NREM-OSA presented the shortest total sleep time and the lowest sleep efficiency. NREM-OSA showed shorter sleep latency and REM latency and higher percentage of N1 than those of REM-OSA and the highest proportion of those who slept in a lateral position than other subgroups. NREM-OSA revealed the highest composite score on the Horne and ${\ddot{O}}stberg$ questionnaire. With increased AHI severity, the numbers of apnea and hypopnea events during REM sleep decreased, and the numbers of apnea and hypopnea events during NREM sleep increased. The results of ANCOVA after controlling age, sex, BMI, NC, AC, and AHI showed the lowest sleep efficiency, the highest AHI in the supine position, and the highest percentage of waking after sleep onset in NREM-OSA. Conclusion: REM-OSA was associated with the mild form of OSA, female sex, and negative emotions. IND-OSA was associated with the severe form of OSA. NREM-OSA was most closely related to position and showed the lowest sleep efficiency. Sleep stage-dependent characteristics could provide better understanding of OSA.

• Sleep Medicine and Psychophysiology
• /
• v.15 no.2
• /
• pp.77-81
• /
• 2008

Introduction: REM sleep which shows characteristic muscle atonia and increased resistance of upper respiratory track is known to be vulnerable to sleep apnea. Previous studies reported that REM sleep-dependent (or related) obstructive sleep apnea syndrome (REM-dependent OSA) could be one of sleep disordered breathing. The present study aimed to investigate clinical findings and polysomnographic variables of REM-dependent OSA. Methods: Fifty-six patients diagnosed with mild to moderate obstructive sleep apnea by overnight polysomnography (5$53.7{\pm}16.7$ years, 42 males). REM-dependent OSA was defined as AHI-REM/AHI-NREM ratio>2. We compared clinical and polysomnographic findings between REM-dependent OSA and No REM-dependent OSA patients. Results: Among 56 patients, 37.5% (n=21, average age of $52.3{\pm}19.7$ years, 14 males) met the REM-dependent OSA criteria. There were no significant differences in age, sex and body mass index between two groups. After controlling for age, sex, body mass index and periodic leg movements index, REM-dependent OSA patients showed significantly lower AHI, lower number of oxygen desaturation events and higher stage 2 sleep proportion compared to No REM-dependent OSA patients (p=0.010, p=0.006, p=0.031, respectively). After controlling for age, sex, body mass index and periodic legs movements index, AHI-REM was positively correlated with the number of oxygen desaturation events in REM-dependent OSA group (p=0.002). Conclusion: Current results suggested that 37.5% of patients with mild to moderate severity of obstructive sleep apnea could be classified into REM-dependent OSA. REM-dependent OSA was more common in mild severity of OSA, equally prevalent in both sexes and accompanied with sleep architecture changes, i.e. increased proportion of stage 2. In addition, apneic events during REM sleep in REM-dependent OSA were related to oxygen desaturation.