What we're learning about the science of sleep

How many hours of sleep did you get last night? If you woke up feeling slightly less than refreshed, join the club: The Centers for Disease Control reports that more than a third of American adults don't get enough sleep.

But as scientists are discovering, chronic under-sleeping can cost you big in the long run. Sleep doesn't just contribute to vitality, it "resets" your brain — and poor sleep has even been linked to Alzheimer's disease and other forms of dementia.

MPR News host Kerri Miller ran down the latest in sleep science with Dr. Yo-El Ju, an assistant professor of neurology at Washington University in St. Louis, and Matthew Walker, a professor of neuroscience and psychology at UC Berkeley, and director of UC Berkeley's Center for Human Sleep Science. Walker's new book is titled "Why We Sleep."