Correlation between Heart Rate Variability and Disease Severity in Obstructive Sleep Apnea

Objective: This study aimed to investigate the variations in Heart Rate Variability (HRV) among individuals with Obstructive Sleep Apnea (OSA) and to explore the relationship between HRV, respiratory parameters, and disease severity. Methods: This prospective study included sixty participants diagnosed with OSA. Polysomnography (PSG) was utilized to assess HRV parameters, including time-domain and frequency-domain measures. Participants were categorized based on the severity of OSA, and data on hemoglobin (HGB), C-reactive protein (CRP), triglyceride (TG) levels, and nocturnal oxygen desaturation (NOD) were collected. Statistical analyses were performed to evaluate the correlations between HRV, respiratory parameters, and disease severity. Results: Among the participants, 23 (38%) had severe OSA, while 17 (28%) were habitual snorers (HS). Hemoglobin, C-reactive protein, and triglyceride levels were significantly higher in patients with severe OSA and NOD compared to HS individuals (p=0.002). Increased Epworth Sleepiness Scale (ESS) scores were associated with higher heart rates during sleep in severe OSA patients compared to HS individuals. NOD (+) patients exhibited statistically higher heart rates during sleep compared to NOD (-) patients (p=0.008). Individuals with an apnea/hypopnea index (AHI) >30, NOD (+), and the lowest SpO2 percentage overnight had significantly lower HRV compared to HS and NOD (-) individuals. Conclusions: In addition to AHI, NOD and the lowest overnight SpO2 are significant markers of elevated cardiovascular risk and are useful for assessing HRV. These findings suggest that cardiovascular risks in OSA patients are heightened both during sleep and wakefulness. Therefore, individuals with severe symptoms, especially those with excessive daytime sleepiness, high levels of NOD, and low nocturnal SpO2 percentages, should be prioritized for treatment, alongside those with high levels of severe OSA.