We all know that going to bed early is healthy. Scientists say the healthiest time is between 10pm and 11pm. Six years ago, the scientists looked at the sleeping and waking times of 80,000 people. They then checked their health for six years. Many people who went to bed earlier than 10pm or later than 11pm got heart disease.

A scientist spoke about how our body clock affects our heart. He said going to bed early or late could change our body clock. This may be bad for our heart. He said our body liked to wake up to morning light. He said the riskiest sleeping time was after midnight because the body may not see the morning light.