The study, published in the European Respiratory Journal, is based on analyses of registry data, collected in the European database ESADA, on a total of some 20,000 adult patients with obstructive sleep apnea (OSA). About 2 per cent of them also had a cancer diagnosis.
"It's reasonable to assume that sleep apnea is a risk factor for cancer or that both conditions have common risk factors, such as overweight. On the other hand, it is less likely that cancer leads to sleep apnea," said Ludger Grote, Professor at the University of Gothenburg in Sweden.
According to the researchers, advanced age was associated with elevated cancer risk, but adjusting the data for age, gender, body mass index (BMI), smoking and alcohol consumption nevertheless showed a possible link between intermittent hypoxia at night and higher cancer prevalence.
The connection applied mainly to women and was weaker in men.
"Our results indicate a cancer risk that's elevated two- to three-fold among women with pronounced sleep apnea," Grote said.
The condition of sleep apnea is well known to the general public and associated with snoring, daytime fatigue, and elevated risk of cardiovascular disease, especially in men, said the study.
This research paves the way for a new view that sleep apnea may possibly be connected with increased cancer risk, especially in women.
"Above all, the focus has been on the connection with one form of cancer: malignant melanoma. Cancer of the breast or womb may now become a new area. There may 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," Grote concluded.
( With inputs from IANS )