NREM-AHI greater than REM-AHI versus REM-AHI greater than NREM-AHI in patients with obstructive sleep apnea: clinical and polysomnographic features.

PURPOSE: Previous studies show a high prevalence of obstructive sleep apnea (OSA) patients with a higher non-rapid eye movement (NREM) apnea-hypopnea index (AHI) (NREM-AHI) than rapid eye movement (REM) AHI (REM-AHI). However, the clinical significance of this phenomenon in patients with OSA is unknown. This study aimed to investigate whether there were significant differences in clinical and polysomnographic features between the NREM-AHI > REM-AHI group and the REM-AHI > NREM-AHI group and to determine whether NREM-AHI > REM-AHI or REM-AHI > NREM-AHI is a specific clinical entity.

METHODS: One hundred forty-two patients with OSA, including 114 males and 28 females, were assessed for specific sleep-related complaints using a semistructured clinical questionnaire, for daytime sleepiness using the Epworth Sleepiness Scale (ESS), for depression using the Beck Depression Inventory (BDI), and for health-related quality of life using the Medical Outcomes Study Short-Form 36 Health Survey questionnaire (SF-36). Anthropometric, clinical, and polysomnographic characteristics were examined between patients with NREM-AHI > REM-AHI and those with REM-AHI > NREM-AHI.

RESULTS: A higher NREM-AHI than REM-AHI was found in 54.9% of the 142 patients with OSA. Overall, males predominated in each group, and there were no significant differences in age, body mass index, medical history, and drug intake between the NREM-AHI > REM-AHI group and the REM-AHI > NREM-AHI group. A high occurrence of NREM-AHI > REM-AHI (94.9%) or REM-AHI > NREM-AHI (90.6%) was found in moderate-to-severe cases each group. Although several indexes of OSA were worse in the NREM-AHI > REM-AHI group than in the REM-AHI > NREM-AHI group, no significant differences in specific sleep-related complaints, ESS score, BDI score, the incidence of daytime sleepiness or depression, and scores of sub-dimensions and the total score on SF-36 were present between the two groups. As compared separately, no significant differences in clinical features were observed in the clinical data for males and females between the two groups.

CONCLUSIONS: Our results show that either NREM-AHI > REM-AHI or REM-AHI > NREM-AHI is more common in moderate-to-severe OSA cases, and there are no significant differences in clinical features between the NREM-AHI > REM-AHI group and the REM-AHI > NREM-AHI group. These findings may suggest that either NREM-AHI > REM-AHI or REM-AHI > NREM-AHI should be considered as a part of the spectrum of OSA, rather than a specific clinical entity.