Comparative Study of HRV Indexes Between Severe and Non-Severe Obstructive Sleep Apnea Patients

Abstract

Background: The temporary cessation of breathing, or obstructive sleep apnea, is a known risk factor for cardiovascular disease. The autonomic cardiac measurement via the heart rate variability (HRV) is a known identification method for heart conditions during sleep, which identifies their relationship with the apnea-hypopnea index (AHI), and can help to detect disease severity. Additionally, it helps to estimate the risk of heart problems and begin treatment of the disease (according to the HRV), and in mild cases, the AHI can help reduce the risk of cardiovascular problems in patients. Objectives: This study was conducted to compare the HRV in patients with severe and non-severe obstructive sleep apnea. Patients and Methods: This cross-sectional study contained 36 patients suffering from obstructive sleep apnea who were referred to the sleep clinic of the Imam Khomeini hospital in Tehran, Iran, in 2015. Apnea syndrome in these patients was confirmed by polysomnography, and the participants were divided into two groups, severe (AHI ≥ 30) and non-severe (AHI = 5 - 29). The age, BMI, resting heart rate, and obtained HRV indexes via a sleep test (polysomnography) were recorded for each patient. The statistical analysis was done by SPSS version 19. Results: The statistical analysis did not show any significant differences in the age and BMI between the two groups. Moreover, the results showed that only the SDNNi index (P value = 0.026) and ODI index (P value = 0.001) were significantly different between the two groups. The AHI had the greatest correlation with the HRV-triangular index (P = 0.022, rp = 0.371), between the HRV indexes, and with the oxygen desaturation index (ODI) (P = 0.001, rp = 0.63), among all of the parameters. Conclusions: According to the results of this study, the majority of the HRV indexes did not significantly differ between the two groups, with only the ODI index differing significantly. Therefore, it seems that a clinical judgment cannot be made based on the index data in all societies.