Rapid eye movement (REM)-related obstructive sleep apnea and hypertension: insights from the clinical spectrum of apnea-hypopnea index ratios across REM and non-REM sleep stages in a Chinese cohort

Previous studies have linked sleep-disordered breathing during rapid eye movement (REM) sleep to hypertension. However, no standardised definition of REM-related obstructive sleep apnea (REM-OSA) exists. This study aimed to evaluate whether the ratio of the apnea-hypopnea index (AHI) in REM to that in non-REM (NREM) (REM-AHI/NREM-AHI) accurately identifies patients with OSA comorbid with hypertension. We screened 1439 participants and included 790 patients with OSA. REM-OSA was defined as AHI >= 5 events/h, REM-AHI/NREM-AHI >= 2, and REM stage >= 30 min. Differences between REM-OSA and NREM-OSA groups, and among quartiles of REM-AHI/NREM-AHI, were assessed. The impact of REM-AHI/NREM-AHI on hypertension was assessed by logistic regression and restricted cubic spline analysis. Overall, patients with REM-OSA, as traditionally defined, had a lower hypertension prevalence, lower blood pressure, and milder OSA. Patients with REM-AHI/NREM-AHI <2 but a higher total AHI had a higher prevalence of hypertension. The highest REM-AHI/NREM-AHI quartile had the mildest OSA and the lowest hypertension prevalence. In subgroups restricted by total AHI or NREM-AHI, a similar trend existed, suggesting that total AHI appeared more influential on hypertension than the predominance of REM-AHI. Restricted cubic spline analysis certified a non-linear relationship between REM-AHI/NREM-AHI and total AHI, blood pressure and hypertension prevalence. Our research showed that patients with REM-OSA defined by REM-AHI/NREM-AHI >= 2 are not the subgroup with the highest hypertension prevalence within the entire OSA population. It is important to avoid focusing solely on the REM-AHI/NREM-AHI ratio and overlooking the overall severity of OSA, which could lead to missing groups that also have a high prevalence of hypertension.