ObjectiveTo investigate the clinical features of patients suffering from obstructive sleep apnea hypopnea syndrome (OSAHS) during little rapid eye movement (REM) sleep, and explore the significance of little REM sleep.MethodsClinical data of 717 patients suffering from OSAHS confirmed with polysomnography (PSG) were analyzed retrospectively. According to the percentage of the REM sleep from the total, all the patients were divided into 2 groups: group A (REM＜20%, n=522) and group B (REM≥20%, n=195). The parameters including patients' age, body mass index (BMI), apnea hypopnea index (AHI), apnea index (AI), hypopnea index (HI), the lowest oxygen saturation (LSaO2), desaturation index (DI), and microarousal index (MAI) were compared between the two groups, respectively. A binary logistic regression analysis was made to investigate the parameters inducing little REM sleep in OSAHS.ResultsThere was no significant difference in patients' age between the two groups (P>0.05). The values of BMI, AI, HI, AHI, LSaO2, DI and MAI in group A were higher than those in group B, and the differences were all statistically significant (all P<0.05). The binary logistic regression analysis revealed statistical differences in LSaO2 (P=0.026, OR=1.038, 95%CI［1.005-1.073］), DI (P=0.047, OR=1.037, 95%CI［1.000-1.075］), MAI（P=0.000，OR=0.887，95%CI［0.833-0.943］) between the two groups．ConclusionsThe OSAHS condition in patients during little REM sleep is more serious than that during normal REM sleep. The main causes of little REM sleep in OSAHS are recurrent hypoxia and arousal.