Impact of severity of obstructive sleep apnea (OSA) and body composition on redox status in OSA patients

Background/Aim. There is an increasing number of studies on the existence of systemic oxidative stress in patients with obstructive sleep apnea (OSA) which is an important mechanism linking OSA and endothelial dysfunction with increased risk for cardiovascular diseases. Comorbidities must be also considered, especially obesity, as the most important source of oxidative stress independently of OSA. The aim of this paper was to show if OSA severity increases the level of markers of systemic oxidative stress and reduces antioxidant capacity, independently from body mass index (BMI) and nutritional status. Methods. One hundred and twenty-eight patients with OSA were included in the trial. Based on the results of a sleep study-polysomnography, the examinees were divided into two groups according to apnea- hypopnea index (AHI < 15 and AHI ≥ 15). Nutritional status was estimated by using the BMI and body composition. Body composition was determined by dual X-ray absorptiometry (DXA) whole-body scan. Redox status of patients with OSA was determined by measuring the concentration of NO in plasma and antioxidant capacity was evaluated using the plasma level of reduced glutathione (GSH) as a marker of antioxidant capacity. Results. Significantly higher mean values of NO were found in the group with AHI ≥ 15 in comparison to AHI < 15 group (1.269 ± 0.789 vs. 0.462 ± 0.373 nmol/mL, respectively; p = 0.001), while significantly higher levels of GSH were found in the group with AHI < 15 in comparison to AHI ≥ 15 group (238.08 ± 84.37 vs. 172.77 ± 83.88 mg/mL, respectively; p = 0.04). Independent predictors of plasma GSH level (multivariate regression analysis) were: desaturation index (ODI) [B = - 0.157; 95% confidence intervals (CI): -0.262–0.053], mean SatO2 (B = -4.76; 95% CI: -9.21–0.306) and min SatO2 (B = 0.118; 95% CI: 0.03–0.206). ODI was singled out as an independent predictor of NO concentration in plasma (B = 0.038; 95% CI: 0.011–0.065). No significant statistical difference was found in mean values of BMI and body composition parameters in patients with AHI < 15 and AHI ≥ 15. None of the markers of systemic oxidative stress was associated with BMI and body composition assessment parameters. Conclusion. OSA severity is significantly associated with reduced antioxidant capacity and increased level of systemic oxidative stress. The degree of desaturation during sleep considerably affects systemic oxidative stress in patients with OSA independently from nutritional status and body composition