Spanish researchers analysed over 5,600 patients from seven different sleep clinics in Spain to investigate the link between sleep apnea and cancer mortality.
The severity of sleep apnea, was then measured, using an hypoxaemia index.
This index measures the amount of time during the night that a person suffers from low levels of oxygen in the blood (less than 90 per cent oxygen saturation).
The results showed that people with sleep apnea who spent more than 14 per cent of their sleep with levels of oxygen saturation below 90 per cent (usually severe sleep apnea patients) had approximately double the relative risk of death due to cancer, than people without sleep apnea.
The results showed that this association was even higher in men and younger people.
"We found a significant increase in the relative risk of dying from cancer in people with sleep apnea. This adds to evidence presented earlier this year that found for the first time a link between cancer and sleep apnea mortality. Our research has only found an association between these disorders but this does not mean that sleep apnea causes cancer," lead author, Dr Miguel Angel Martinez-Garcia from La Fe University Hospital in Valencia, Spain, said in a statement.
Another study found an increase in all-type cancer incidence in people with severe sleep apnea.
In a third study, researchers used a mouse model of skin cancer (melanoma) to investigate tumour spread (metastasis) and whether this was associated with sleep apnea.
The results showed that the spread of cancer was more abundant in mice that had been subjected to intermittent hypoxic air, with low levels of oxygen as in sleep apnea, than those who breathed normal air during the experiment.
"The data from this study in animals strongly suggests a link between the spread of cancer and sleep apnea," lead author, Professor Ramon Farre from University of Barcelona in Spain, said.
The studies were presented at the European Respiratory Society's (ERS) Annual Congress in Vienna.
