Sleep apnea affects both men and women. But women with a severe form of this sleep disorder are at greater risk of developing cancer, according to new research published in the European Respiratory Journal, reports the University of Gothenburg in Sweden.

Researchers analyzed data from a total of about 20,000 adults with obstructive sleep apnea, a potentially serious form of the sleep disorder that occurs when throat muscles intermittently relax and block a person’s airway during sleep. About 2% of those included in the study also had a cancer diagnosis.

After adjusting for several factors such as age, gender and body mass index, findings showed a statistically significant link between intermittent hypoxia (low oxygen in the body’s tissues) at night and higher cancer prevalence.

“Our results indicate a cancer risk that’s elevated two- to threefold among women with pronounced sleep apnea,” said Ludger Grote, adjunct professor of pulmonary medicine at Sahlgrenska Academy at the University of Gothenburg. “It’s impossible to say for sure what causes underlie the association between sleep apnea and cancer, but the indication means we need to study it in more in depth.”

According to Grote, possible causes of elevated cancer risk in women with sleep apnea could be a “combined effect of female sex hormones and stress activation, induced by nocturnal hypoxia in sleep apnea, that can trigger cancer development or a weakening of the body’s immune system.”

Scientists will begin investigating potential sleep apnea connections with specific cancers including malignant melanoma, breast cancer and endometrial cancer.

For related coverage, read “How Does Sleep Affect Our Cancer Risk?” by Cancer Health blogger Michael Breus, PhD; “Sleep Solutions”; and “Getting Back in the Boat.”