National Research Institute of Tuberculosis and Lung Disease (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran TANAFFOS (Respiration) 1735-0344 23 4 2024 10 01 Heart Rate Variability in Obstructive Sleep Apnea: Association with Excessive Daytime Sleepiness and Cardiovascular Risk 371 375 728971 EN Besharat Rahimi Thoracic Research Center, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran 0000-0003-0193-3243 Niloofar Khoshnam Rad Thoracic Research Center, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran 0000-0001-6700-3570 Tayebe Mohammad Alizade Thoracic Research Center, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran 0009-0004-3534-3887 Somaye Mohammadi Department of Cardiology, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran 0009-0001-2045-5948 Shahram Firoozbakhsh Thoracic Research Center, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran 0009-0008-3108-5795 Journal Article 2023 10 29 <strong>Background: </strong>Obstructive sleep apnea (OSA) is associated with increased vagal activity, sympathetic nervous system activation, and cardiovascular complications. Excessive daytime sleepiness (EDS) in OSA patients is a predictor of cardiovascular and all-cause mortality. Heart rate variability (HRV) can be used to assess cardiac autonomic modulation, which is affected by OSA. This study aimed to evaluate the relationship between HRV and daily sleepiness in OSA patients based on the excessive sleep scale (ESS) scores. <strong>Materials and Methods: </strong>The study included 70 patients with OSA, divided into two groups: those with EDS (ESS ≥ 11) and those without sleepiness (ESS < 11). Time and frequency domain parameters were evaluated. The results were compared and analyzed between the two groups. <strong>Results: </strong>Patients with OSA and EDS had higher cardiovascular risk, as indicated by different HRV parameters (higher low-frequency parameter and higher time domain parameters), compared to non-sleepy OSA patients. A significant positive correlation was found between ODI and AHI with VLF, and significantly higher LF and VLF in EDS patients. <strong>Conclusion: </strong>OSA patients with EDS had higher cardiovascular risk, as indicated by different HRV parameters, compared to non-sleepy OSA patients. A significant positive correlation was found between ODI and AHI with VLF, and significantly higher LF and VLF in EDS patients. Further studies are needed to better understand the relationship between HRV and daily sleepiness in patients with OSA. https://www.tanaffosjournal.ir/article_728971_c157948f529ff2def21d6fdd72e479dd.pdf