More than 50 million Americans struggle with chronic sleep disorders, according to the American Academy of Sleep Medicine. New research suggests that being in tune with the body's circadian rhythm -- a 24-hour internal clock that regulates sleep cycles -- is crucial for our health. Dr. Jennifer Martin, president of the American Academy of Sleep Medicine, joins John Yang to discuss. PBS NewsHour is supported by - https://www.pbs.org/newshour/about/funders