Effect of nocturia in patients with different severity of obstructive sleep apnea on polysomnography

Objective: Obstructive sleep apnea (OSA) is one of the etiologies of nocturia. We analyzed polysomnography (PSG) results to determine correlated factors related to nocturia in OSA patients with different severity. Methods: Patients with suspected OSA were examined using PSG. They were divided into two groups based on the presence of nocturia. Nocturia was defined as a patient who needed to void at least once. Apnea–hypopnea index (AHI) was employed to classify patients according to degrees of severity: AHI<5 events/h, 5 events/h≤AHI<15 events/h, 15 events/h≤AHI<30 events/h, and AHI≥30 events/h, defined as normal, mild OSA, moderate OSA, and severe OSA, respectively. Demographic variables, PSG parameters, International Prostate Symptom Scores (IPSSs), and quality of life scores due to urinary symptoms were analyzed. Results: In total 140 patients, 114 patients had OSA (48 had mild OSA; 34 had moderate OSA; and 32 had severe OSA) and 107 patients had nocturia. The total IPSS was significantly higher in nocturia patients in all groups except the group of severe OSA patients. With the increasing severity of OSA, more correlated factors related to nocturia were determined. In mild OSA patients, nocturia related to increased age (p=0.025), minimum arterial blood oxygenation saturation (p=0.046), and decreased AHI of non-rapid eye movement (p=0.047), AHI of total sleep time (p=0.010), and desaturation index (p=0.012). In moderate OSA patients, nocturia related to increased age (p<0.001), awake time (p=0.025), stage 1 sleep (p=0.033), and sleep latency (p=0.033), and decreased height (p=0.044), weight (p=0.025), and sleep efficiency (p=0.003). In severe OSA patients, nocturia related to increased weight (p=0.011), body mass index (p=0.009), awake time (p=0.008), stage 1 sleep (p=0.040), arousal number (p=0.030), arousal index (p=0.013), periodic limb movement number (p=0.013), and periodic limb movement index (p=0.004), and decreased baseline arterial blood oxygenation saturation (p=0.046). Conclusion: Our study revealed that there were more correlated factors related to nocturia with increasing severity of OSA. This study helps in clinical education and treatment for OSA patients with different severity.