Severe breathing disorders during sleep, such as sleep apnea, can kill, a study in more than 6,000 people shows.

Men 40 to 70 years old with severe sleep-disordered breathing were twice as likely to die over an eight-year period as their peers without the condition, Dr. Naresh Punjabi of Johns Hopkins University in Baltimore and his colleagues found.

Sleep-disordered breathing is characterized by the collapse of the upper airway during sleep leading to numerous, brief interruptions of breathing known as sleep apnea. It is associated with high blood pressure and heart disease, Punjabi and his team note in the journal PLoS Medicine.

About one in four men and one in ten women have sleep-disordered breathing, but the condition goes undiagnosed in 70% of patients, Punjabi noted in an email to Reuters Health.

In the Sleep Heart Health Study, Punjabi and colleagues assessed nighttime breathing, sleep patterns and blood oxygen levels of 6,441 men and women aged 40 and older at the study’s outset who were not initially receiving treatment for sleep apnea.

During follow-up, which averaged 8.2 years, 1,047 people died.

People with severe sleep-disordered breathing, the researchers found, were nearly 1.5 times more likely to die during follow up than those without sleep-disordered breathing, even after controlling for age, race, body weight, high blood pressure, diabetes, heart disease and smoking status.

The risk was especially great for men 40 to 70 years old, who were roughly two times more likely to die during follow up if they had severe sleep-disordered breathing. While sleep-disordered breathing also increased men’s risk of death from cardiovascular disease, it didn’t affect women’s likelihood of dying from heart disease.

“The relation between sleep apnea and higher risk of death seems to be from the repeated decreases in oxygen levels during sleep,” Punjabi said. “Low oxygen levels during sleep can trigger a cascade of events…which can lead to high blood pressure, heart disease, stroke, and diabetes.”

The current standard treatment for sleep apnea is continuous positive airway pressure (CPAP), in which a person wears an oxygen mask during sleep to help push air into the lungs. But 30% to 40% of patients can’t tolerate CPAP, according to Punjabi. For these patients devices worn in the mouth or even surgery are options, he added, but aren’t always effective, while surgery can be risky, too.

Weight loss is likely the best option, Punjabi added, because it usually leads to improvement of sleep apnea symptoms and in some cases a complete cure.

He and his colleagues are now planning to investigate sleep apnea and mortality in women, because the current study included too few women with severe sleep disordered breathing and too few deaths among women to draw definitive conclusions.

They conclude their report by calling for clinical trials to investigate whether treating sleep apnea will reduce mortality.

SOURCE: PLoS Medicine, August 17, 2009.