It was a single team of scientists doing these studies. It all started when they noticed that thirty or so people who had suddenly died during sleep had hearing loss in their right ear. They subsequently made a patent for a device about sixteen years ago which measures the vital signs of deaf or hearing impaired people as they sleep. The scientists said in the patent that the inner ear sound detecting cells are chemoreceptors (special cells which make us breathe autonomously – super important). They later did studies on mice which proved this hypothesis and in the press releases the scientists concluded that hearing loss/ear damage is a cause of sudden death.