Neurocognitive Decline in Rapid Eye Movement (REM)-Predominant Obstructive Sleep Apnea (OSA) Versus Non-rapid Eye Movement (NREM)-Predominant OSA: A Comparative Study.

OBJECTIVE: The present study aims to investigate the distribution and characteristics of obstructive events across rapid eye movement (REM) and non-rapid eye movement (NREM) sleep stages and to assess their clinical and neurocognitive implications in patients with obstructive sleep apnea (OSA) in an Indian population. METHODOLOGY: This comparative study was conducted at the Department of Respiratory Medicine, Rajarajeswari Medical College and Hospital, Bangalore, from January to June 2025. It included 50 suspected OSA patients, screened using the STOP-BANG questionnaire. All participants underwent level 1 polysomnography and were classified as having either REM-predominant or NREM-predominant OSA based on the American Academy of Sleep Medicine (AASM) criteria. Neurocognitive and depression assessments were performed using the Mini-Cog test and the Patient Health Questionnaire-9 (PHQ-9). Statistical analysis was conducted using IBM SPSS Statistics for Windows, Version 22.0. The Mann-Whitney U test was applied for group comparisons, and a p-value of <0.05 was considered statistically significant. RESULTS: The study included 50 patients, comprising 30 (60%) male patients and 20 (40%) female patients. Among the male patients, 27 (90%) had NREM-predominant OSA, while three (10%) had REM-predominant OSA. Among the female patients, 13 (65%) had NREM-predominant OSA, whereas seven (35%) had REM-predominant OSA. Female patients were more frequently presented with fatigue, whereas snoring was more commonly reported among male patients. The mean age was 50.63 ± 16.19 years for the NREM group and 52.80 ± 13.02 years for the REM group. The mean body mass index (BMI) was 30.47 ± 5.49 kg/m² in NREM OSA and 53.27 ± 63.43 kg/m² in REM OSA. The mean heart rate was 72.05 ± 8.22 beats per minute (bpm) in NREM OSA and 75.70 bpm in REM OSA. The NREM apnea-hypopnea index (AHI) was 5.27 ± 2.63 in REM OSA and 35.56 ± 29.17 in NREM OSA, with significantly higher values in the latter (p = 0.0001). The Mini-Cog score was considerably lower in REM OSA (1.30 ± 1.34) compared to NREM OSA (4.00 ± 1.28) (p = 0.0001). The PHQ-9 score was significantly higher in REM OSA (12.40 ± 4.20) than in NREM OSA (3.48 ± 2.70) (p = 0.0001). CONCLUSION: The detrimental effects of REM-predominant OSA on cognitive function are linked to reduced intracranial oxygen supply, fragmented sleep, and elevated oxidative stress and inflammation. Maintaining continuous positive airway pressure use in the early morning hours, when patients are most prone to discontinuation, is essential for optimal management. Our study emphasizes the need for neurocognitive screening in all newly diagnosed REM-predominant OSA patients to help prevent serious comorbidities. Early and appropriate intervention may mitigate the progression of neurocognitive impairment.