Tehran University of Medical Sciences Journal of Sleep Sciences 2476-2938 4 3-4 2020 07 01 59 62 Besharat Rahimi Advanced Thoracic Research Center, Tehran University of Medical Sciences, Tehran, Iran Anahita Tavoosi Advanced Thoracic Research Center, Tehran University of Medical Sciences, Tehran, Iran Toktam Sadeghi Advanced Thoracic Research Center, Tehran University of Medical Sciences, Tehran, Iran Romina Arjmand Advanced Thoracic Research Center, Tehran University of Medical Sciences, Tehran, Iran Maryam Edalatifard Advanced Thoracic Research Center, Tehran University of Medical Sciences, Tehran, Iran 2018 12 06 2019 11 13 Background and Objective: Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder and an important risk factor for cardiovascular diseases (CVDs). This study aimed to compare abnormal heart rate and arrhythmias among patients with OSA and normal subjects. Materials and Methods: This case-control study was conducted on patients with OSA who were attending Imam Khomeini Hospital Sleep Lab, Tehran, Iran, to undergo a full-night polysomnography (PSG). Apnea-Hypopnea Index (AHI) was measured for study participants. Those with AHI < 5/h were considered as control (normal) and those with AHI > 15/h were considered as case (OSA) group. We compared abnormal heart rate and nocturnal arrhythmia during PSG between the two study groups. Results: A total of 60 patients (30 cases and 30 controls) were included in this study. Abnormal heart rate (bradycardia and tachycardia) and nocturnal arrhythmia were compared between the two study groups. Twenty-eight percent of patients with moderate to severe OSA developed arrhythmia including sinus arrest, premature atrial contraction (PAC), atrial fibrillation (AF), and bigeminy premature ventricular contraction (PVC). Multiple PVC episodes were observed in 6.7% of subjects without OSA. Nocturnal arrhythmia was more common in cases; however, there was no significant difference. Mean heart rate in cases was 45 beat/minute in comparison with 68/minute in controls (P = 0.0001). Conclusion: Different arrhythmias are observed in patients with OSA due to autonomic disorders. Bradycardia was more prevalent among patients with OSA. Regarding the association between OSA and nocturnal arrhythmias, treatment of OSA is important to prevent cardiac mortality. https://jss.tums.ac.ir/index.php/jss/article/view/120