Objective:To analyze the sleep quality and sleep structure of patients with obstructive sleep apnea hypopnea syndrome (OSAHS) complicated with patent foramen ovale (PFO), and to study the effect of PFO on the sleep structure of OSAHS.Methods:Fifty-six patients with OSAHS complicated with PFO, 64 patients with simple OSAHS and 62 controls were collected from December 2018 to March 2020 in Centre of Sleep Disorders, the Second Affiliated Hospital of Zhengzhou University. Pittsburgh Sleep Quality Index and polysomnography were used to compare the sleep quality and sleep structure of the three groups.Results:Compared with the control group [6/62(9.68%)], OSAHS complicated with PFO group [54/56(96.43%)] and simple OSAHS group [53/64(82.81%)] had higher incidence of poor sleep quality (χ2=112.08, P<0.0l). Furthermore, compared with the control group, the OSAHS complicated with PFO group and simple OSAHS group showed reduced sleep efficiency [PSQI total score was 0.5 (0, 1), 2 (1, 3) and 2 (1, 2) respectively, H=74.549, P<0.01] and reduced proportions of rapid eye movement (REM; 20.45%±3.49%, 12.19%±5.95% and 15.11%±7.21%,respectively, F=21.17, P<0.01) and slow wave sleep (N3; 21.24%±4.12%, 14.15%±6.08%, 17.68%±6.35%, respectively, F=29.51, P<0.01); the N1 (4.47%±2.40%, 9.50%±5.34%, 9.55%±4.61%, respectively, F=30.07, P<0.05) and N2 sleep (53.88%±4.35%, 64.09%±7.49%, 58.14%±6.67% , respectively, F=46.21, P<0.05) were prolonged; the inocturnal lowest oxyhemoglobin saturation (SpO 2) level was lower, mean SpO 2 reduction at night was higher [3.00% (0, 4.00%),6.00% (5.00%, 8.75%) and 4.00% (4.00%, 5.00%), respectively, H=72.24, P<0.05], and periodic leg movement index [16.30(4.80, 32.82), 33.30(9.26, 54.80) and 23.10(8.38, 31.83),respectively, H=17.86, P<0.05], arousal index [11.60(7.73, 17.55), 23.90(14.03, 30.45) and 15.6(11.23, 20.78), respectively, H=22.80, P<0.05] and sleep apnea and hypopnea index (AHI; 1.60±1.38, 23.90±7.27 and 16.24±4.22,respectively, F=136.97, P<0.05) increased. Compared with the simple OSAHS group, the incidence of poor sleep quality was higher, the proportions of slow wave sleep (N3, F=29.51, P=0.047) and REM ( F=21.17, P=0.012) were decreased, N2 sleep ( F=46.21, P=0.000) was prolonged, mean SpO 2 reduction at night ( Z=54.28, P=0.000), wake after sleep onset [116.00(89.88, 143.00) min vs 135.00(118.50, 168.38) min, Z=25.71, P=0.023], arousal times [14.00(8.25, 8.00) vs 17.50(9.00,23.00),respectively, Z=19.68, P=0.041], microarousal ( Z=23.57, P=0.044), and AHI ( F=136.97, P=0.000) were increased in the OSAHS complicated with PFO group. Conclusions:OSAHS complicated with PFO patients had poor sleep quality and high incidence of sleep disorders. They had sleep disorder at night, which was characterized by the decrease of REM sleep and slow wave sleep, the prolongation of N2, the decrease of nocturnal SpO 2 and the increase of awakening times, and the increase of arousal times and AHI. PFO can aggravate the sleep disorder of OSAHS.