Obstructive Sleep Apnea Severity Correlates with Cellular and Plasma Oxidative Stress Parameters and Affective Symptoms

Obstructive sleep apnea syndrome (OSAS) is considered a sleep-related respiratory disorder, characterized by repetitive episodes of complete (apnea) or partial (hypopnea) obstruction of airflow in the upper airway (UA) during sleep. The pathophysiology of upper airway obstruction in OSAS is multifactorial, leading to a chronic recurrent state of intermittent hypoxemia and reoxygenation during sleep, maintaining a state of oxidative stress, which seems to be the key to the pathophysiological manifestations of OSAS, and is associated with the development of a number of high morbidity-mortality systematic complications, such as obesity, type 2 diabetes, metabolic syndrome, and cardiovascular and neuropsychological diseases. This study is an open, cross-sectional, and comparative clinical trial, whose general objective was to assess the correlation between OSAS severity, oxidative stress markers, and the presence of affective symptoms (depressive and anxious) in OSAS patients. We studied 38 adult males, who had been diagnosed with OSAS by overnight polysomnography, between 18 and 60 years of age, divided into three groups: group 1-10 individuals with mild OSAS (AHI between 5 and 14.9/h), group 2-13 individuals with moderate OSAS (AHI between 15 and 30/h), and group 3-15 individuals with severe OSAS (AHI > 30/h). All individuals were evaluated for level of subjective sleepiness using the Epworth Sleepiness Scale, for depressive and anxiety symptoms by the Hamilton Depression (HAM-D) and Anxiety (HAM-A) Scales, and for parameters of the oxidative stress state, measuring superoxide radical and serum nitrates and nitrites levels. There was a progressive and significant increase in the state of oxidative stress (p < 0.05), in the total score of depressive symptoms (p = 0.001) and in the overall score of anxiety symptoms (p = 0.004) directly proportional to the severity of apnea when comparing the mild group to the severe group. Positive correlations were identified between superoxide production and the apnea-hypopnea index (AHI) (r = 0.48), Epworth sleepiness score (r = 0.36), and Hamilton depression score (HAM-D) (r = 0.40); between serum nitrates and nitrites levels and SO2 min (r = 0.44); and between the AHI and the HAM-D (r = 0.51) score and HAM-A (r = 0.40) score. Negative correlations were observed between the AHI and serum nitrates and nitrites levels (r = -0.42), between superoxide production and SO2 min (r = -0.31), between serum nitrates and nitrites levels and HAM-D (r = -0.50) and HAM-A (-0.42) scores, and between SO2 min and HAM-D (r = -0.48) and HAM-A (r = -0.40) scores. According to the results of this study, we can conclude that (1) individuals with OSAS show an increase in the production of superoxide radical and a decrease in serum nitrates and nitrites levels, which are objective signs of a state of oxidative stress. (2) The more severe the OSAS, the more fragmented the sleep and the greater the nocturnal hypoxemia, the more severe is the oxidative stress state and the greater is the incidence of daytime symptoms, especially sleepiness and depressive and anxiety symptoms. Future studies might explore the investigation of oxidative stress parameters as an alternative approach to anticipate symptoms, measure prognosis, and monitor OSAS progression or treatment response.