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Sleep Med. 2003 May;4(3):225-8.

Antioxidant capacity in obstructive sleep apnea patients.

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Pulmonary Department, Medical School, University of Thessaly, 22 Papakyriazi, 41222 Larissa, Greece.



Obstructive sleep apnea syndrome (OSA) results in oxygen desaturation and arousal from sleep. Free oxygen radicals are highly reactive molecules, which can be produced by the OSA phenomenon known as hypoxia/reoxygenation. Hypoxic conditions, such as OSA, may also result in transient depletion of cellular reductants, which constitute a main line of antioxidant defense. Both apneas and hypopneas usually end in arousal, where reoxygenation causes the production of reactive oxygen species (free radicals). Living organisms have developed complex antioxidant systems to counteract reactive oxygen species and to reduce their damage. We evaluated the antioxidant capacity in serum from OSA patients and healthy people in order to confirm the hypothesis that there is a relationship between oxidative stress and OSA.


A physician interviewed 25 participants, determining age, smoking habits and symptoms such as excessive daytime sleepiness and snoring. Physical examination and polysomnography were performed during patients' hospitalization. Antioxidant capacity was measured in blood samples by Trolox Equivalent Antioxidant Capacity assay.


Seventeen out of 25 subjects had an apnea/hypopnea index (AHI) greater than 10 (OSA group). The measurement of antioxidant capacity did not differ between the OSA patients and our healthy sample (of 25 subjects, seven with an AHI less than 10). Furthermore, patients with severe OSA (AHI >20, N=14) had linearly negative correlation between antioxidant capacity in their blood samples and AHI (R=-0.551, P=0.041).


Reduced antioxidant capacity in serum is an index of excessive oxidative stress. Patients with severe OSA have reduced values of antioxidant capacity.

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