People with a common sleep-breathing disorder "have diminished activity among neurons responsible for keeping heart rate low," their heart rate regulation, according to a recent study.

Researchers George Washington University found that in obstructive sleep apnea (OSA), neurons in the brainstem that control heart rate experience a blunting of their activity. The reduction of neuronal activity likely contributes to the increased heart rate, blood pressure and risk of adverse cardiovascular events that occur in these patients.

The sleep disorder is a common cardiovascular disease that causes repetitive interruptions of breathing during sleep. Lack of oxygen during these episodes brings the person to a lighter state of sleep or brief wakefulness to restore normal breathing. Cycles of interrupted breathing and arousal from sleep can occur as frequently as once per minute.

"Lack of sleep leaves the mind and body tired, leading to poor mental and physical performance, and if untreated [obstructive sleep apnea] increases a person's risk of developing hypertension and irregular heartbeats. Therefore it is very important that we have discovered some of the underlying mechanisms that could injure the heart and other cardiovascular tissues," David Mendelowitz, leader of the study, said in a statement.

For the study, researchers mimicked obstructive sleep apnea for four weeks in rats and studied the changes in blood pressure, heart rate, and synaptic activity in parasympathetic neurons that control heart rate.

"Our study shows that progression of blunted cardiovascular reflexes is accompanied, and likely maintained by, inhibition of neurons in the brainstem that protect the heart and normally maintain a low resting heart rate," Mendelowitz said. "This study would predict that patients who have [obstructive sleep apnea], and also take sleep medicines, might be at heightened risk for an exaggerated reduction of essential neuronal activity that protects the heart."

The sleep-breathing conditions occur in 24 percent of adult males and 9 percent of adult females.

The findings were recently published in The Journal of Physiology.