Person sleeping with an Oura ring (IMAGE) University of California - San Diego Caption Researchers signled out five types of sleep based on analyses of five million nights across roughly 33,000 people wearing an Oura ring. Credit OURA Usage Restrictions Please credit License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.