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.