A sleep-related disorder that causes repeated interruptions in breathing is a new risk factor for death from stroke, Spanish researchers said Tuesday.

Sleep apnea affects about 20 percent of people. Sufferers can stop breathing for 10 seconds or more while asleep, sometimes more than 300 times a night.

Dr Olga Parra and researchers at Barcelona University Hospital in Spain monitored 161 stroke patients and found that their risk of dying from a stroke was linked to sleep apnea.

“It’s the first time the link between apnea and stroke has been shown to affect mortality,” Parra said.

The link was most clear in patients with obstructive sleep apnea, when breathing may be interrupted because the upper airways collapse.

Parra and her colleagues began monitoring the breathing of stroke patients shortly after they were admitted to hospital following strokes and calculated an apnea index for each one.

During the 30-month study, 22 patients died. Half of them had suffered a second stroke. The higher the patient scored on the apnea scale, the greater the risk of dying from stroke, the researchers said in the study reported in the European Respiratory Journal.

Stroke is a leading killer worldwide and occurs when a blood vessel to the brain bursts or is blocked by a clot, cutting off vital oxygen. In 2002, an estimated 5.5 million people worldwide died from strokes, according to the World Health Organization.

“This Spanish study represents a milestone in our understanding of the potential role of sleep apnea in stroke patients,” Ludger Grote, of the Sahlgrenska Hospital in Sweden, said in a commentary in the journal.

“Its results could have considerable implications for the future management of stroke,” he added.

Parra and her team did not explain why sleep apnea raises the risk of stroke death but they said the disorder can be treated by using a nasal mask that supplies a continuous flow of pressurized air to reduce the breathing interruptions.

They have now launched a study in several centers in Spain to see if treating sleep apnea could cut the death rate from stroke. The results of that study are expected in about five years.