Obstructive sleep apnea and blood pressure. Interaction between the blood pressure-lowering effects of positive airway pressure therapy and antihypertensive drugs.

BACKGROUND: There is increasing evidence that obstructive sleep apnea is an independent risk factor for arterial hypertension. Previous studies on the antihypertensive effects of positive airway pressure therapy on daytime blood pressure (BP) revealed inconsistent results.
METHODS: The relations between the apnea/hypopnea index (AHI) and BP or heart rate (HR) were investigated in a cohort of 540 consecutive patients (age, 55.4 +/-11.1 years) with moderate or severe obstructive sleep apnea (OSA). The mean AHI was 28.2 +/- 22.0 events/h before OSA therapy. A group of 196 patients in whom antihypertensive medication was kept unchanged was followed for 6 months during bilevel or continuous positive airway pressure (Bi-/CPAP) therapy.
RESULTS: Significant associations were found between AHI and systolic BP (beta = 0.078, P = .014), diastolic BP (beta = 0.056, P = .003), HR (beta = 0.096, P < .001), and the prevalence of arterial hypertension (odds ratio = 0.015, P = .003), independent of age, body mass index, and gender. During the follow-up period with effective Bi-/CPAP therapy, the mean daytime systolic BP decreased from 130.7 +/- 15.5 mm Hg to 128.6 +/- 15.9 mm Hg (P = .051), diastolic BP from 80.2 +/- 9.3 mm Hg to 77.5 +/- 9.5 mm Hg (P = .001), and HR from 77.7 +/- 8.8 to 75.7 +/- 8.1 beats/min (P = .001). Multiple linear regression analysis revealed that the absence of antihypertensive drugs and the level of the initial BP are significant and independent predictors for the lowering effect of Bi-/CPAP therapy on systolic and diastolic BP.
CONCLUSIONS: This study confirms an independent relationship between the severity of OSA and BP/HR. Absence of BP-lowering medication and BP values before treatment are independent predictors for the reduction of BP with Bi-/CPAP therapy.