Antioxidant status in patients with sleep apnoea and impact of continuous positive airway pressure treatment

The episodes of hypoxia/re-oxygenation associated with the respiratory disturbances observed in patients with obstructive sleep apnoea syndrome (OSAS) may induce the generation of oxygen free radicals. Indeed, several studies suggest that OSAS is associated with oxidative stress. The present study tested the hypothesis that patients with OSAS have an alteration in antioxidant defences. The plasma levels of total antioxidant status (TAS), glutathione peroxidase (GPX), gamma-glutamyltransferase (GGT), vitamins A, E, B-12 and folate, and homocysteine were determined in 47 patients with OSAS and 37 healthy subjects. Of these, 27 patients who used continuous positive airway pressure (CPAP) for > 4 h(.)night(-1) were re-examined 12 months later. Patients with OSAS had lower TAS (1.4 +/- 0.16 versus 1.50 +/- 0.10 mmol(.)L(-1)), vitamin A (64 +/- 19 versus 74 +/- 17 mu g(.)dL(-1)) and vitamin E levels (1,525 +/- 499 versus 1,774 +/- 503 mu g(.)dL(-1)), and increased values of GGT (42 +/- 22 versus 32 +/- 16 (UL-1)-L-.) than controls. There was no difference between groups in GPX, homocysteine, vitamin B12 and folate plasma levels. CPAP treatment normalised the levels of TAS (1.50 +/- 0.13 mmol(.)L(-1)) and the activity of GGT (30 +/- 14 (UL-1)-L-.) without any influence on vitamins levels. In conclusion, the results indicate that patients with obstructive sleep apnoea syndrome have a decreased antioxidant capacity that is partially reversed by continuous positive airway pressure treatment.