A hi-tech ring worn on a finger at night could detect sleep apnoea, a potentially dangerous snoring 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.