What is the connection between sleep apnea and high blood pressure?

The connection between sleep apnea and heart disease is a complicated one. The causal connection is not clear, but we do know that those with sleep apnea today have a high chance of developing hypertension in the future. In fact, people with cardiovascular problems—especially high blood pressure, heart failure, and stroke—have a higher prevalence of sleep apnea.

This fact makes sense because those with obstructive sleep apnea put their bodies under more stress because the condition prevents proper rest to occur on a daily basis. Obstructive sleep apnea (OSA) is when the upper throat closes, and the patient stops breathing numerous times during the night, putting them at risk for developing vascular disease that causes a specific type of treatment-resistant form of high blood pressure.

One of the problems with defining the connection between OSA and heart disease is that people with the former condition often have other complicating diseases as well.

When treating people with high blood pressure and sleep apnea, or heart failure and sleep apnea, the measures of blood pressure or heart failure are significantly improved. This suggests there is a cause-and-effect relationship between hypertension and sleep apnea.

Nancy Kanagy, PhD, a professor in the University of New Mexico (UNM) Department of Cell Biology and Physiology, is researching to understand how the connection occurs.

Insight is on the horizon

Just how sleep apnea heightens blood pressure demands further research, but we do know that up to one in five people may suffer from it. Recently, the National Institutes of Health issued a call for proposals on sleep apnea research on the connection several years ago. Kanagy realized UNM’s experience in conducting vascular studies could provide much needed insight here.

“Most researchers were looking at the sympathetic nervous system,” Kanagy says in a release. “We thought, ‘Why not develop a model to investigate vascular changes and contributions to the elevated blood pressure?”

Kanagy’s discovered a key connection when her team developed a rat model of sleep apnea and discovered that after 14 days of repeated exposure to hypoxia during sleep increases blood pressure, even during waking hours. Hypoxia is a condition when the body or a region of the body is deprived of an adequate supply of oxygen. The researchers found that hypoxia increases production of an artery-constricting peptide called endothelin, and this peptide elevates blood pressure. Further studies are investigating exactly how that happens.

Her team is further investigating how hydrogen sulfide molecules (H2S) play a crucial role in controlling blood pressure. In the study, they found that sleep apnea patients show significantly lower H2S levels compared with normal sleepers. This molecule appears to limit inflammation and open arteries, which leads to relieving the cardiac and vascular systems from constriction.

“Long-term, we are hoping that a better understanding of these mechanisms will lead to new and more effective therapies to treat cardiovascular disease in sleep apnea patients,” Kanagy says.