Narrator: This is Science Today. It's a common belief that getting 8 hours of sleep per night is required for optimal health. But sleep specialist Daniel Kripke of the University of California, San Diego's School of Medicine, conducted a six-year study of more than a million adults and found those who slept 8 hours or more per night had an increased death rate compared to those who only slept 6 to 7 hours.
Kripke: I don't want to scare people. The person who sleeps 8 hours instead of 7 isn't going to die much sooner - on average, only a couple of months. So it isn't something to worry about very much. These data are simply a guidance for us - that we don't need to try to sleep more than about 7 hours. And that's good news because the average in the population today is about 6 ½ hours sleep on weekdays. So really, these studies show that what the average American is doing is close to ideal.
Narrator: For Science Today, I'm Larissa Branin.