Treatment of obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) may also lower blood pressure among hypertensive adults, according to researchers in Spain, who will present his findings at the American Thoracic Society’s 2008 International Conference in Toronto on Sunday, May 18.

The study included 394 consecutive patients with high blood pressure and non-sleepy OSA—those with mild enough OSA that their daytime alertness was unaffected. They were randomized to receive either CPAP or no treatment.

Blood pressure was measured at three-, six- and 12-month follow-ups after their baseline evaluation. The researchers found that, on average, patients who used the CPAP machine experienced an average 2mmHg drop in both systolic and diastolic blood pressure at the end of the year when compared to patients who did not use the CPAP machine.

“This is the largest study trial in the field and it shows hat CPAP has an effect on cardiovascular outcomes regardless of symptoms,” said Ferran E. Barbé, MD, who headed the research. “This suggests that CPAP can not only be used to treat the symptoms of sleep apnea (daytime sleepiness), but also to reduce cardiovascular risk in apneic patients.”

The patients for whom the effect was most produced used the CPAP machine for more than five hours a night. “The mechanism by which CPAP is able to effect a drop in blood pressure is complex and it is mainly related to a reduction in sympathetic tone, oxidative stress,” explained Barbé.

Although researchers do not yet know whether CPAP should be recommended for all OSA patients with high blood pressure and without daytime sleepiness, barring contraindications, the results point to the need for further study of the cardiovascular benefits of CPAP in OSA patients.

“In the future, we would like to know the effects of CPAP treatment on other cardiovascular outcomes such as stroke, myocardial infarction or heart failure,” said Barbé.