Better sleep and lower blood pressure

Studies performed at the Heart Institute, InCor, show that treatment of sleep apnea can reduce blood pressure in patients with resistant hypertension as well as prevent evolution of the disease.

By Fábio de Castro

Agência FAPESP – In studying cases of resistant hypertension (cases that do not improve even with medication) a group of researchers found that the condition most commonly associated with the problem is sleep apnea—a condition characterized by heavy snoring and choking while the patient sleeps. In the study, the scientists found that, curiously, most of the patients with sleep apnea did not know they had it.

The study was performed by scientists at the Heart Institute (InCor) at the Universidade de São Paulo (USP) Hospital das Clinicas Medical School together with researchers from the Instituto Dante Pazzanese de Cardiologia, and has already been accepted for publication in Hypertension magazine.

In another innovative study, the InCor group also showed that the use of CPAP equipment (Continuous Positive Airway Pressure), the standard treatment for sleep apnea, can be efficient as auxiliary therapy in the case of patients with resistant hypertension. A previous study published in March’s edition of Hypertension had shown that CPAP is also efficient as prevention in the case of pre-hypertension or masked hypertension patients.

Both resistant hypertension studies were carried out under a project funded by FAPESP under its Regular Research Awards program and was coordinated by Geraldo Lorenzi Filho, InCor professor. The studies were also coordinated by Luciano Drager, assistant doctor at the InCor Hypertension Unit.

“By definition, the patients with resistant hypertension are those that cannot control their high blood pressure even when taking three anti-hypertensive drugs at the maximum dosage, one of which being a diuretic. It’s a very serious problem, which is why we decided to study this very difficult type of hypertension,” Drager told Agência FAPESP.

In partnership with scientists from the Instituto Dante Pazzanese, the InCor researchers monitored over 100 patients with resistant hypertension in order to investigate the cause. The conclusion was that apnea was the most commonly associated condition.

“We identified a frequency of 64% of sleep apnea in the resistant hypertension population. The apnea was, by far, the main cause of the problem,” said Lorenzi. In a second study with the resistant hypertension population, the InCor researchers separated a random group to be treated with CPAP together with medications, and another group to be treated with medications only over a six month period. This work was part of doctoral research and will soon be submitted to Hypertension.

“The treatment with CPAP provoked a significant reduction in the patients’ arterial pressure. It’s a helpful treatment alternative that doesn’t exclude the use of medications. The result was encouraging,” he said.

Pre-hypertension and masked hypertension

According to Drager, aside from the studies related to patients resistant to the treatment, the group also did a study focused on the opposite case: patients with pre-hypertension or masked hypertension. “We already knew that sleep apnea is a risk factor for the development of hypertension and that CPAP treatment promotes the reduction of arterial pressure. So we began to raise the question: if we use CPAP in patients at risk of developing hypertension, could we prevent it?” he said.

The scientists studied patients with two different types of problems in search of the answer: pre-hypertension and masked hypertension. “These two conditions are factors that increase the risk of the patient developing sustained hypertension in the future,” he affirmed.

According to Drager, pre-hypertension is characterized by individuals with arterial pressure near the limits of hypertension, but still in the normal range. In the cases of masked hypertension, patients’ pressure readings are normal in the doctor’s office, but high when monitored over a 24 hour period.

“We studied 36 patients with significant sleep apnea. Half the group was randomly selected to be treated with CPAP and half had no treatment for three months. We found that at the end of the period, the group that received the CPAP treatment showed a considerable reduction in pre-hypertension and masked hypertension,” he said.

At the beginning of the study, 94% of the patients with sleep apnea also had hypertension. After the CPAP treatment, only 55% still had the problem. And 39% began the study with masked hypertension, a number that dropped to 5% after the CPAP treatment.

The group that didn’t receive the CPAP treatment showed no significant change. “Among those treated with CPAP, the reduction of hypertension and masked hypertension was quite significant, considering there were only three months of treatment,” said Drager.

Sleep apnea patients don’t sleep well, snore, have compromised memories and sleepiness during the daytime, all of which call for treatment. But the study’s main message, according to the scientist, is that aside from the improvement in quality of life brought on by the reduction of apnea symptoms, CPAP treatment could, in theory, prevent the occurrence of hypertension.

“Investment in apnea treatment with CPAP could be an alternative for reducing hypertension among the general population, having a clear positive economic impact on public resources,” he pointed out.

The article The Effects of Continuous Positive Airway Pressure on Prehypertension and Masked Hypertension in Men With Severe Obstructive Sleep Apnea (doi:10.1161/HYPERTENSIONAHA.110.165969), by Luciano Drager, Geraldo Lorenzi Filho and others can be read by Hypertension subscribers at: http://hyper.ahajournals.org.