Sleep apnoea has been linked with an increased likelihood of dying from cancer, according to new research.

Spanish scientists have shown that the more severe a person's sleep apnoea, the higher their risk of perishing from cancer.

Studies also found a link between the spread of cancer and sleep apnoea.

Sleep apnoea is a condition in which a person stops breathing for more than ten seconds while sleeping.

In the first study, over 5,600 patients from seven different sleep clinics in Spain were analysed to investigate the link between sleep apnoea and cancer deaths.

The severity of sleep apnoea in the patients was 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.

The results showed that people with sleep apnoea who spent more than 14% of their sleep with levels of oxygen saturation below 90% (usually severe sleep apnoea patients) had approximately double the risk of dying from cancer than people without sleep apnoea. The results showed that this association was even higher in men and younger people.

People with sleep apnoea can be treated using continuous positive airway pressure (CPAP) therapy, which generates a stream of air to keep the upper airways open during sleep. In the first study, patients who were not using this device consistently had an increased relative risk of death from cancer.

"We found a significant increase in the relative risk of dying from cancer in people with sleep apnoea," said Dr Miguel Angel Martinez-Garcia from La Fe University Hospital in Spain, who led the study.

"This adds to evidence presented earlier this year that found for the first time a link between cancer and sleep apnoea mortality. Our research has only found an association between these disorders but this does not mean that sleep apnoea causes cancer."

Similar results were also found in a second study, which showed an increased presence of cancer in people with severe sleep apnoea. The link was present even when factors such as age, sex, weight and other comorbidities of participants, were taken into account.

The research, which was presented at the European Respiratory Society's (ERS) annual congress in Vienna, adds to evidence presented earlier this year highlighting a link between severe sleep apnoea and cancer.