Abnormally increased endothelin-1 in plasma during the night in obstructive sleep apnea: Relation to blood pressure and severity of disease

Background: The mechanisms involved in development and maintenance of hypertension in obstructive sleep apnea (OSA) are not clarified. We hypothesize that patients with OSA have an abnormal nocturnal level of some vasoactive hormones during the night. Methods: We studied 32 patients with OSA and 19 healthy control subjects during The night-time with serial determinations of endothelin-I (ENDO-1), angiotensin II (Ang II), renin (PRC), aldosterone (ALDO) in plasma, and blood pressure (BP), and oxygen saturation. Results: Patients with OSA had a higher plasma level of ENDO than healthy controls and the mean nocturnal level of ENDO correlated significantly to the apnea-hypopnea index (AHI) as a measure of the severity of OSA. This correlation remained statistically significant after analysis in a general linear model with correction for confounders. Patients with OSA also had a significantly higher BP than healthy controls and the ambulatory BP correlated positively to the AHI in patients with OSA. No significant differences were measured in Ang II, PRC, and ALDO between the two groups. The correlation between AHI and ENDO supports OSA as a stimulus of endothelin release or increased endothelin levels contributing to the severity of OSA. Conclusions: Endothelin seems to be a pathogenic factor in generating hypertension in OSA.