 All right, here we go with the latest on sleep. Once we reach middle age, experts say we need to sleep a certain number of hours every night to maintain good health. And that number happens to be seven hours, no more, no less. Researchers at the UK's University of Cambridge found that was the optimal amount of sleep for cognitive performance. The data also showed that more or less than seven hours of sleep, more or less, was linked to reduced mental processing speed and problem-solving skills.