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24-05-2012 | Article

Choice of CPAP for prevention of hypertension in sleep apnea - a tossup?



MedWire News: Two new studies provide conflicting data on the benefits of continuous positive airway pressure (CPAP) for preventing or controlling hypertension in patients with obstructive sleep apnea (OSA). The studies appear in the current issue of JAMA.

In the first, Ferran Barbé (Institut de Recerca Biomedica, Lleida, Spain), and co-authors in the Spanish Sleep and Breathing Network randomly assigned 725 consecutive patients with OSA but no daytime sleepiness to CPAP or no active intervention.

They defined OSA as an apnea-hypopnea index of 20 episodes per hour or more. The participants had an Epworth Sleepiness Scale score of 10 or less, indicating no daytime sleepiness. The primary endpoints were incidence of systemic hypertension or cardiovascular events.

An analysis of follow-up data (median 4 years) on all patients who were available for analysis (357 assigned to CPAP and 366 controls) showed that 68 patients on CPAP had newly diagnosed hypertension, and 28 had one or more cardiovascular events, including 17 unstable anginas or arrhythmias, one nonfatal stroke, three heart failures, two nonfatal myocardial infarctions (MIs), two transient ischemic attacks (TIAs), and one cardiovascular death.

In all, 79 patients in the control group had new hypertension and 31 had cardiovascular events (11 unstable anginas or arrhythmias, eight nonfatal MIs, five TIAs, five heart failures, and two nonfatal strokes).

The incidence density rate for either hypertension or cardiovascular events among patients in the CPAP group was no different from that among controls, at 9.20 versus 11.02 per 100 person-years.

"This study suggests that in patients with OSA and without daytime sleepiness, the prescription of CPAP compared with usual care did not result in a statistically significant reduction in the incidence of hypertension or cardiovascular events," Barbé et al write.

They note that a post hoc analysis suggested that CPAP might reduce the incidence of hypertension and/or cardiovascular events in patients who use it for 4 hours or longer each night.

In the other study, researchers from the USA and Spain led by José Marin (Hospital Universitario Miguel Servet, Zaragoza, Spain) looked at 1889 patients without hypertension who were referred to a sleep center for nocturnal polysomnography from 1994 through 2000, and followed them for a median of 12.2 years.

Among patients with OSA treated with CPAP, the crude incidence of hypertension per 100 person-years was 3.06, compared with 5.12 for patients with OSA who were prescribed CPAP but were nonadherent, 5.84 in patients with OSA who declined CPAP, 3.34 for patients with OSA ineligible for CPAP, and 2.19 for controls (patients without OSA).

In multivariate models adjusted for confounding factors including age, gender, baseline systolic and diastolic blood pressure, lipids, drugs, change in body mass index censored for time, and other factors, they found that the risk for hypertension was significantly greater than for controls among patients with OSA who declined (hazard ratio [HR]=1.96), were ineligible for (HR=1.33), or were nonadherent to CPAP (HR=1.78). By contrast, the risk was lower than for controls among CPAP-treated OSA patients (HR=0.71).

Marin and co-authors conclude that "compared with participants without OSA, untreated OSA was associated with an increased risk of new-onset hypertension, whereas treatment with CPAP therapy was associated with a lower risk of new-onset hypertension."

By Neil Osterweil