Optic disc and retinal nerve fiber layer parameters as indicators of neurodegenerative brain changes in patients with obstructive sleep apnea syndrome.

PURPOSE: Retina is a unique part of the central nervous system (CNS) for visualizing the processes of axonal and neuronal degeneration. Optical coherence tomography (OCT) allows direct visualization and measurement of retinal nerve fiber layer (RNFL) thickness, macular volume, and optic disc (OD) parameters. One of the disorders associated with atrophy in different brain regions is obstructive sleep apnea syndrome (OSAS). In the present study, we aimed to determine OD and RNFL changes measured by OCT for investigating the progress of neurodegeneration development in OSAS, excluding all the other conditions that can directly affect RNFL thickness and optic nerve parameters. METHODS: Both eyes of 101 patients with OSAS and 20 controls were investigated by OCT. Full-night polysomnography (PSG) and ophthalmologic examination including automated visual field (VF) examination and OCT were performed in all of the patients. RESULTS: According to the OSAS grading, patients were grouped as mild (n=15), moderate (n=27), and severe (n=59). We found significant decrease in RNFL thickness only in the patients with severe OSAS compared with the other groups and decreased macular ganglion cell thickness in the severe OSAS group compared with the control group. VF parameters were significantly worsened in all the OSAS subgroups compared to the control group. We found different data such as normal or increased optic nerve parameters as result of subtle OD edema, which may mask possible peripapillar axonal loss. CONCLUSIONS: We think that evaluation of neurodegeneration in OSAS is not always possible by examining OD and RNFL because there are difficulties due to the confounding issues of cerebral atrophy and OD edema.

Low serum copeptin levels in patients with obstructive sleep apnea.

PURPOSE: Copeptin, the C-terminal fragment of antidiuretic hormone (ADH), is a new biomarker that has been found to be elevated in several cardiovascular disorders and is related with prognosis. Patients with obstructive sleep apnea demonstrate a tendency to develop coronary and cerebral atherosclerotic disease. Our aim was to investigate copeptin levels in untreated new diagnosed obstructive sleep apnea patients without manifest cardiovascular disorders in order to determine whether copeptin could be used as a biomarker in this group. METHODS: A total of 60 patients with obstructive sleep apnea, diagnosed with polysomnography, and 23 healthy volunteers were enrolled into this study. Blood samples were collected after overnight fasting, and copeptin level was measured with an enzyme immunoassay method. RESULTS: Patients with obstructive sleep apnea had a higher incidence of hypertension and body mass index but lower serum copeptin level (0.48 ± 0.24. vs. 0.64 ± 0.28 ng/ml, p = 0.007) compared with the healthy controls. There was no significant difference regarding to serum copeptin levels between the moderate (n = 13) and severe (n = 47) obstructive sleep apnea patients (0.42 ± 0.18 vs. 0.49 ± 0.26 ng/ml, p = 0.409). CONCLUSIONS: Rather than reflecting a reduced risk for cardiovascular disorders, we consider that reduced copeptin level is related with disturbed ADH secretion in obstructive sleep apnea patients. Therefore, it would not be advisable to measure copeptin levels in obstructive sleep apnea patients to determine cardiovascular risk, while this marker could be valuable to demonstrate impairment in ADH regulation in this patient group.