A lack of sleep can seriously affect people's performance but just one good night's sleep can more or less restore you to normal. Researchers from the University of Pennsylvania studied 159 healthy adults who had an average age of 30. The participants were divided into groups and were allowed different amounts of sleep. Every two hours, while they were awake, they completed a 30-minute computerized test. Those whose sleep had been restricted were found to have a shorter attention span, be less alert and have slower reactions. However, people's performance went back to normal after just one full night's worth of sleep. Another study of more than 30,000 adults in the same journal - Sleep - found that the optimum amount of sleep for good health is seven hours a night. People who had less than five hours a night had double the risk of cardiovascular disease while those getting more than nine hours also had a higher risk.
You can find out more about this study by clicking on the link in the title of this post.