Objective To explore the changes in plasma angiotensin II (Ang II) and circadian rhythm of blood pressure among hypertensive patients with sleep apnea syndrome (SAS) before and after continuous positive airway pressure (CPAP) or surgical treatment. Methods A total of 180 essential hypertension patients were enrolled in our study. The determination of plasma Ang II concentration

ambulatory blood pressure (ABP)

and polysomnography (PSG) monitoring were performed before and 3 months after CPAP or surgical treatment. Results Patients were classified into three groups by their apnea-hypopnea index (AHI): essential hypertension group (EH group

n=72; AHI<5)

essential hypertension with mild SAS group (EH+mild SAS group

n=60

5≤AHI<20)

and essential hypertension with moderate and severe SAS group (EH+moderate-severe SAS group

n=48

AHI≥20). The concentrations of plasma AngⅡ in the above three groups were 13.42±3.27

16.17±3.82

and 18.73±4.05 ng/mL respectively before treatment

and AngⅡ concentration in EH patients combined with SAS was significantly higher than that in EH group (all P<0.05). After treatment the values in the latter two groups significantly decreased to 14.67±2.56 and 15.03±3.41 ng/mL respectively (P<0.05). The incidence of non-dipper blood pressure curve in EH patients was 31.9%

and those in hypertensive patients with mild SAS and moderate-severe SAS were 51.7% and 58.3%

respectively before treatment. The incidence of non-dipper blood pressure curve in the EH patients with mild SAS was significantly higher than that of patients with EH alone (P<0.05). After CPAP treatment or surgery

the incidence of non-dipper blood pressure curve in the two SAS groups was significantly decreased to 38.3% and 39.6%

respectively (P<0.05). Conclusions Ang II might play a role in blood pressure variability in patients with obstructive SAS. CPAP or surgical treatment can improve blood pressure disorder and decrease plasma Ang II level in patients with obstructive SAS.