Background: Patients with obstructive sleep apnea (OSA) are at increased risk for hypertension. The mechanisms responsible for the development of hypertension are controversial. We hypothesized that patients with OSA had an abnormal 24-h blood pressure (BP) and an abnormal activity in vasoactive hormones, and that both BP and hormones were normalized during treatment with long-term nasal continuous positive airway pressure (CPAP).
Methods: The 24-h BP and plasma levels of the vasoactive hormones (renin, angiotensin II, aldosterone, atrial natriuretic peptide, brain natriuretic peptide, vasopressin, and endothelin-1) were measured in 24 patients with OSA and in 18 control subjects. Thirteen patients with OSA were reexamined after 14 months of CPAP therapy.
Results: Patients with OSA had significantly increased BP and heart rate and a reduced nocturnal BP drop. Both angiotensin II (13.3 +/- 1.6 v 7.8 +/- 1.0 pmol/L) and aldosterone (94.0 +/- 9.4 v 62.2 +/- 4.5 pmol/L) were significantly higher in OSA than in control subjects. Positive correlations were found between angiotensin II and daytime BP (systolic: r = 0.49, P <.01; diastolic: r = 0.52, P <.01). The CPAP therapy resulted in a decrease in BP, and this CPAP-induced reduction in BP was correlated with a decrease in both plasma renin (r = 0.76 to 0.92, all P <.01) and plasma angiotensin II concentration (r = 0.58 to 0.81, all P <.05).
Conclusions: Plasma angiotensin II and aldosterone were elevated in OSA, and plasma angiotensin II was correlated with BP. Long-term CPAP reduced BP, and this decrease in BP was correlated with the reductions in plasma renin and angiotensin II levels. We suggest that OSA mediates hypertension, at least in part, via a stimulation of angiotensin II production.