Objective: The aim of this study was to compare serum copeptin levels in patients with obstructive sleep apnea syndrome (OSA) and simple snorers without sleep apnea; and to investigate relationships between copeptin levels and polysomnographic parameters.

Methods: Serum copeptin levels were determined using enzyme-linked immunosorbent assay in 47 patients with OSA and 12 patients without OSA (control group). Full-night polysomnography was performed in each patient. Patients with OSA were divided into three groups according to their Apnea Hypopnea Index (AHI) scores: mild OSA (5 < AHI < 15), moderate OSA (15 < AHI < 30), and severe OSA (AHI > 30).

Results: A total of 59 patients were included in the study. There were 23 female (39.0%) and 36 male (61.0%) subjects. The range of ages of study subjects was between 27 and 63 (mean 44.75 ± 9.64) years. According to the AHI values, patients were classified into four groups: simple snoring (n = 13), mild OSA (n = 10), moderate OSA (n = 15), and severe OSA (n = 21). Statistically significant differences between AHI groups in terms of age, Epworth score, and neck circumference. According to multiple comparison results for age, the difference between simple snoring and moderate OSA was statistically significant. According to multiple comparison results for Epworth score, the difference between simple snoring and severe OSA was statistically significant. According to multiple comparison results for neck circumference, a similar result was found like Epworth Sleepiness Scale score. The difference between AHI groups by gender was tested by a Pearson χ(2) test and was found to be statistically significant. There was no statistically significant difference among AHI groups in terms of copeptin. There was a statistically significant correlation of copeptin with AHI during rapid eye movement (REM) sleep; however, the correlation coefficient was not sufficiently large.

Conclusions: Increased serum copeptin concentration may reflect a response to stress in some diseases. This is well documented especially in cardiovascular diseases; however, we could not find any difference in OSA groups in terms of copeptin levels.