12.11.2013
by Salynn Boyles
Contributing Writer, MedPage Today

Among obstructive sleep apnea patients with resistant hypertension, treatment with continuous positive airway pressure (CPAP) lowered both daytime and nighttime blood pressure in a multicenter, clinical trial.

Patients in the study who had acceptable CPAP adherence showed clinically and statistically significant reductions in both 24-hour mean and diastolic blood pressure, especially during the night, according to Miguel-Angel Martinez-Garcia, MD, PhD, of the Hospital Universitario y Politecnico La Fe in Valencia, Spain, and colleagues.

“Obstructive sleep apnea (OSA) is highly prevalent in patients with resistant hypertension, regardless of other confounding variables such as the presence of obesity, thus suggesting this subgroup of hypertensive patients is a potential worthwhile population for CPAP treatment,” the researchers wrote in the Dec. 11 issue of the Journal of the American Medical Association.

Drug-Resistant High BP Common in OSA

Compared with control patients who did not receive CPAP or received sham CPAP, patients with resistant hypertension treated with CPAP achieved greater decreases in 24-hour mean blood pressure over 12 weeks of treatment (3.1 mm Hg, 95% CI 0.6-5.6,P=0.02) and greater reductions in diastolic blood pressure (3.2 mm Hg, 95% CI 1.0-5.4,P=0.005).

Between 12% and 27% of patients with hypertension require at least three anti-hypertensive drugs to control their blood pressure, and are considered to have resistant hypertension.

OSA affects between 4% and 6% of the general middle-age population, but a 2001 studysuggested that more than 70% of patients with resistant hypertension have the sleep breathing disorder. Because of this, OSA is now recognized as one of the most prevalent risk factors for resistant hypertension.

Treatment with CPAP is recognized as an effective strategy for lowering blood pressure, but it has not been clear if this effect is more pronounced in patients with resistant hypertension, the researchers wrote.

A small, randomized trial published in early November found that CPAP treatment significantly lowered daytime blood pressure in patients with moderate-to-severe OSA and resistant hypertension.

But the 40-patient study failed to show significant reductions in nocturnal blood pressure or nocturnal dipping in patients treated with CPAP.

1 in 4 Patients Had Nighttime BP Dips

The new study included 194 patients with OSA (apnea-hypoxia index (AHI) of 15 or higher) who also had resistant hypertension. They were randomized to receive either treatment with CPAP or no treatment for OSA while maintaining usual blood pressure medications.

Participants were recruited from 24 teaching hospitals in Spain from June of 2009 to October of 2011.

The mean age of the patients was 56, 69% were men, and the mean BMI was 34.1. The average AHI score was 40.4 events per hour, and the patients took, on average, 3.8 drugs for hypertension.

Mean baseline 24-hour blood pressure was 103.4 mm Hg, while baseline systolic and diastolic pressures were 144.2 mm Hg and 83 mm Hg, respectively.

The average use of CPAP treatment was 5 hours a night, with 71 of 98 CPAP-treated study participants (72.4%) using the device at least 4 hours per night.

At baseline, 25.8% of patients displayed a dipper nighttime blood pressure pattern, defined as a 10% or larger drop in average nighttime blood pressure compared with average daytime pressure.

Difference Most Evident at Night

Among the findings:

• Intention-to-treat analysis revealed significant decreases in 24-hour mean blood pressure and diastolic blood pressure among the CPAP-treated patients, but not 24-hour systolic blood pressure (3.1 mm Hg, 95% CI 0.6-6.7, P=0.10)

• The percentage of patients displaying a nocturnal blood pressure dipper pattern at the 12-week follow-up was greater in the CPAP patients than the controls (35.9% versus 21.6%; adjusted OR 2.4, 95% CI 1.2-5.1, P=0.02).

• There was a significant positive correlation between hours of CPAP use and the decrease in 24-hour mean blood pressure (r=0.29, P=0.006), systolic blood pressure (r=0.25, P=0.02) and diastolic blood pressure (r=0.30,P=0.005).

• In a per-protocol analysis involving 71 CPAP and 87 control patients, the CPAP group showed a statistically significant decrease in 24-hour mean blood pressure of 4.4 mm Hg (95% CI 1.8-7.0, P=0.001), a decrease in systolic blood pressure of 4.9 mm Hg (95% CI 1.2-8.6, P=0.01), and a decrease in diastolic blood pressure of 4.1 mm Hg (95% CI 1.9-6.4, P<0.001).

“This difference was more evident during the night, with a decrease of 7.1 mm Hg (P=0.003) in nocturnal systolic BP and 4.1 mm Hg (P=0.003) in nocturnal diastolic BP,” the researchers wrote.

Study limitations cited by the researchers included a lack of quantification of the duration of sleep, but they noted that this was unlikely to have affected their results.

They concluded that further research is warranted to examine longer-term health outcomes among this common subgroup of OSA patients with resistant hypertension.

From the American Heart Association:

• AHA/ACCF Sleep Apnea and Cardiovascular Disease