Snoring may cause cancer tumours to grow and spread, a new study has warned.
People who suffer from sleep apnea have far worse cancer outcomes than those who sleep soundly.
The condition occurs when the walls of the throat relax and narrow during sleep, interrupting normal breathing by blocking the airways for 10 seconds or more.
It is suggested this starves vital organs of oxygen, so the body releases a signal protein to form more blood vessels which feed tumours allowing them to grow and spread.
This may explain why those who exercise and get oxygen pumping through their blood may be more protected from cancers than those who lead sedentary lives.
Apnoea is characterised by people snoring loudly with their breathing noisy and laboured, often interrupted by gasping and snorting with each episode.
It starts in the 30s with an estimated four per cent of British middle-aged men and two per cent of middle-aged women having it.
Many cases may go undiagnosed as sufferers may not be aware of their sleep problem.
Previous studies has linked sleep apnoea with an increased risk of high blood pressure and stroke but there was no explanation of the linked to more aggressive cancers.
A new study suggested it could be down to the process known as hypoxia, where a tissue or organ does not get enough oxygen.
The study in mice suggests hypoxia causes an increased production of the protein Vascular endothelial growth factor (VEGF), known to promote blood vessels formation.
Dr Antoni Vilaseca of the Hospital Clinic of Barcelona said: “Patients suffering from obstructive sleep apnoea usually suffer from intermittent hypoxia at night.
“This work shows that intermittent hypoxia has the potential to promote the formation of blood vessels within tumours, meaning that the tumours have access to more nutrients.
“This is of course an early animal study, so we need to be cautious in applying this to humans.
“Nevertheless, this work indicates a plausible mechanism for just why conditions which restrict oxygen flow to tissues, like sleep apnea, may promote cancers”.
The findings were presented at the European Association of Urology Congress in Munich.
Chairman Professor Arnulf Stenzl of Tübingen University commented: “Although this is an experimental study, it is remarkable, because it demonstrates the influence of oxygen deficiency on the growth of renal cell carcinoma tissue - both primary tumour as well as metastases.
“It may be postulated that increased oxygenation of the blood may be the underlying mechanism why not smoking or giving up smoking, regular sport activity (especially endurance type sports), reducing the body mass index and other lifestyle changes that increase tissue oxygenation have a supportive beneficial effect on better outcomes in renal cell cancer as well as other tumour types.”
The study involved mice with kidney tumours who were subjected to varying oxygen levels to mimic intermittent hypoxia.
They showed increases in vascular progenitor cells and endothelial cells within the tumours.
These cells may later mature to form blood vessels in the tumours.
Circulating VEGF was also increased in the mice which had undergone hypoxia, although other factors such as tumour growth, were not affected.