condition which can increases the risk of heart attacks and strokes.
This could make it simpler to diagnose the problem — one charity estimates that almost 80 per cent of cases go undetected.
Sleep apnoea occurs when the muscles in the airways relax to such an extent that they become completely obstructed and breathing is halted for at least ten seconds.
It can be treated with continuous positive airway pressure, where a mask is worn over the face during sleep to keep airways open. But first it must be diagnosed, and this can prove difficult, partly because those affected will be unaware of what they do during sleep.
Until now the options for making an accurate diagnosis include cumbersome home-testing equipment consisting of tight-fitting bands across the chest to measure breathing movements, a heart rate monitor, a breathing sensor over the face and a clip-on oxygen sensor on an index finger.
The other possibility is spending a night in a sleep clinic to have a polysomnography — a test that records brain waves, oxygen levels, heart rate, breathing and even eye and leg movements during sleep.
But the ring could prove far more convenient. Made from soft silicone, it is packed with sensors which track changes in blood oxygen levels as the patient sleeps.
A fall in blood oxygen readings at night is one of the main signs of sleep apnoea. This is because, as the airways momentarily collapse, the amount of oxygen getting into the bloodstream is reduced.
The ring is worn on the middle or ring finger of one hand, where there is a larger volume of blood flowing than in other fingers.
Attached to the ring is a small capsule containing tiny bulbs that beam red light through the skin. This light penetrates tiny blood vessels near the surface and is absorbed by a protein in the blood called haemoglobin, which carries oxygen around the body.