We know that people with Alzheimer's often have sleep problems. But does it work the other way? Do problems with sleep set the stage for this degenerative brain disease? NPR correspondent Jon Hamilton introduces us to some scientists looking into that connection in this updated report on the key role deep sleep may play in maintaining brain health and protecting the brain against Alzheimer's. Follow host Maddie Sofia on Twitter @maddie_sofia. Email the show at shortwave@npr.org.