Patients who have a common breathing problem in their sleep may be at risk of artery damage, suggests research.

Thousands of people suffer from sleep apnoea, a condition in which they stop breathing temporarily during the night.

The problem can disrupt the quality of sleep, and lead to intense fatigue during the day, and has been linked to depression.

Researchers at the Technion-Israel Institute of Technology in Haifa, Israel, studied white blood cells from sleep apnoea sufferers.

They found that they carry many of the same characteristics of white blood cells taken from patients with hardened arteries.

This artery hardening - a process called atherosclerosis - causes them to lose elasticity and thicken, impairing circulation, and perhaps contributing to heart disease.

Both sets of white blood cells were covered in far greater amounts of "adhesion molecules" than normal.

Free radicals

In a test tube, they tended to bind more readily to cells called endothelial cells, normally found lining the walls of blood vessels.

They also tended to produce more "free radical" molecules - which have the potential to inflict damage on cell linings, increasing the artery hardening process yet more.

While there have been studies suggesting that patients with sleep apnoea are more likely to have strokes, congestive heart failure and possibly heart attacks, this finding is the first direct evidence suggesting a physical reason for the link.

Dr David White, director of the Sleep Disorders Program at Brigham and Women's Hospital in Boston, described the study as an "important step forward".

Mask-wearing treatment

He said: "If the firm binding of white blood cells to endothelial cells in the test tube is what happens in the blood of sleep apnoea patients every night, then this may be significant evidence that sleep apnoea is associated with an active process of atherosclerosis."

He suggested that active and effective treatment for the sleep disorder could well halt the process in its tracks.

While some patients undergo surgery to try to ease their night-time breathing, others have a treatment called continuous positive airway pressure (CPAP), in which the patient wears a mask as they sleep, which gently pushes air down the windpipe, keeping the throat open.