People with sleep apnoea, which causes snoring and dangerous pauses in breathing at night, could be twice as likely to die of cancer as those who sleep soundly.
The largest study of its kind found that sufferers with the highest oxygen deprivation were at the greatest risk.
The sleep disorder is already linked to obesity, heart disease, diabetes, daytime fatigue and high blood pressure.
Doctors advise sufferers to have treatment because maintaining oxygen levels at night may reduce the risk of developing related illnesses. The condition causes the muscles in the airway to collapse during sleep, cutting off breathing for ten seconds or more before brain signals force the muscles to work again.
Spanish researchers studied more than 5,600 patients from seven sleep clinics, looking at the duration for which oxygen in a person's blood dropped below 90 per cent at night a measure called the hypoxemia index. The patients, none of whom had a cancer diagnosis when the study began, were followed for seven years.
Researchers found that the greater the extent of hypoxemia, or oxygen depletion, the more likely a person would be to receive a cancer diagnosis during the study period.
Dr Miguel Angel Martinez-Garcia, of La Fe University and Polytechnic Hospital in Valencia, Spain, said the cancer risk increased with the time spent without oxygen.
Severely affected sufferers who spent more than 14 per cent of their sleep with levels of oxygen saturation below 90 per cent had twice the risk of fatal cancer than those without sleep apnoea. The findings were revealed yesterday at the European Respiratory Society congress in Vienna. A second study showed chronic sufferers were two thirds more likely to develop all types of cancer.
Some treatments appear to cut the risks. Patients can sleep wearing a mask over their nose, fed with a stream of air from a bedside pump, ensuring the throat remains open and they get a full nights sleep.
Dr Martinez-Garcia said: Our research has only found an association. This does not mean sleep apnoea causes cancer.
- Daily Mail