SDB covers a range of disorders that lead to interrupted breathing during sleep.

By far the most common is obstructive sleep apnoea, in which the airway collapses, leaving the sleeper struggling for breath. Typically this produces snoring and repeated forced waking.

Sleep apnoea is known to be associated with obesity, diabetes, high blood pressure, heart attacks and strokes.

The latest research from the University of Wisconsin-Madison in the US also points to a connection with cancer mortality.

Scientists looked at 22 years-worth of data on a total of 1,522 people who took part in a study of sleep problems.

Participants underwent tests that included measurements of sleep and breathing at four-year intervals.

The results showed an association with cancer death that increased sharply with SDB severity.

People with mild SDB were just 0.1 times more likely to die from cancer than those without the problem.

But moderate SDB doubled the chances of cancer death, while severe SDB increased the risk 4.8 times.

Study leader Dr Javier Nieto, from the University of Wisconsin School of Medicine and Public Health, said: "The consistency of the evidence from the animal experiments and this new epidemiologic evidence in humans is highly compelling.

"In vitro (laboratory) and animal studies suggest that intermittent hypoxia promotes angiogenesis and tumour growth, which can explain these observations.

"Ours is the first study to show an association between SDB and an elevated risk of cancer mortality in a population-based sample. If the relationship between SDB and cancer mortality is validated in further studies, the diagnosis and treatment of SDB in patients with cancer might be indicated to prolong survival.

"Additional studies are needed to replicate our results and to examine the relationships between SDB, obesity, and cancer mortality."

The findings were presented today at the American Thoracic Society international conference in San Francisco. They will also appear in the American Journal of Respiratory and Critical Care Medicine.

The scientists made adjustments to take account of age, sex, body mass index (BMI - a measurement relating height and weight), smoking and other factors that may have influenced the results.

One surprising discovery was that the association was stronger for non-obese patients than obese patients.

This echoed findings in mice which showed that the effects of intermittent hypoxia on cancer growth was significantly more pronounced in lean animals.

Source: Telegraph