Sleep-disordered breathing -- which includes obstructive sleep apnea -- is linked with an increased risk of dying from cancer, a new study suggests.

Researchers from the University of Wisconsin School of Medicine and Public Health found that people who have severe sleep-disordered breathing are five times more likely to die of cancer than people without the condition.

Sleep-disordered breathing occurs when a person stops breathing during sleep, thereby causing disrupted sleep. Past research has linked the condition with heart risks, as well as metabolic syndrome and insulin resistance, according to the National Institutes of Health.

The study was presented at the American Thoracic Society 2012 International Conference, and will be published in the American Journal of Respiratory and Critical Care Medicine. It included health data on 1,522 people who were part of the Wisconsin Sleep Cohort, which started in 1989.

As part of the study, participants underwent an overnight sleep study every four years. The researchers found that people who had severe sleep-disordered breathing were 4.8 times more likely to die of cancer, compared with people without the condition.

"Clearly, there is a correlation, and we are a long way from proving that sleep apnea causes cancer or contributes to its growth," study researcher Dr. F. Javier Nieto, a sleep epidemiology expert at the University of Wisconsin, said in a statement.

"But animal studies have shown that the intermittent hypoxia (an inadequate supply of oxygen) that characterizes sleep apnea promotes angiogenesis -- increased vascular growth -- and tumor growth," Nieto added. "Our results suggest that SDB is also associated with an increased risk of cancer mortality in humans."

Previously, researchers at the Centers for Disease Control and Prevention found that men with sleep apnea may face a doubled risk for depression and women may face a five times increased risk for depression, compared with those without the condition, Health.com reported.

That study, which was published in the journal SLEEP earlier this year, also showed that not everyone with sleep apnea is receiving a diagnosis of the condition. Health.com reported:

More than 80 percent of the people who reported classic symptoms such as snorting or gasping for breath on most nights of the week had never received an official diagnosis. This group, too, had a threefold higher risk of depression compared to people who had no trouble breathing at night.

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