Research at the University of Miami aims to learn what makes sleep apnea a risk factor for strokes, the Miami Herald reports.

A stroke occurs when the blood supply to part of the brain is interrupted, depriving the brain of oxygen. A stroke may be caused by a narrowed or blocked artery supplying blood to the brain or by a burst blood vessel in the brain.

The interruptions in breathing that characterize sleep apnea lead to low oxygen levels in the blood and brain.

“Sleep apnea triggers a series of responses in the body as a result of low oxygen levels,” Ramos said. “One of them is hypertension — an increase in blood pressure.”

Hypertension associated with sleep apnea occurs because of the strain that low oxygen levels in the blood and brain place on the cardiovascular system. As high blood pressure is an independent risk for stroke, sleep apnea becomes an indirect cause of stroke.

Sleep apnea is most likely to lead to ischemic strokes, the ones caused by an interruption of blood supply to the brain.