'GMA 40 for 40': See Day 1 of Dan Childs' 40-Hour Experiment to Stay Awake

— -- To show you just how important sleep is to a healthy lifestyle, Dan Childs, the managing editor of the ABC News' Medical Unit, is staying awake for 40 hours as part of "Good Morning America's" 40th anniversary line-up of events.

Sleep deprivation is a huge issue in the U.S., with an estimated 50 to 70 million Americans suffering from a chronic sleep disorder, according to the Centers for Disease Control and Prevention. Every month, 40 percent of adults report falling asleep during the day without meaning to at least once, according to the CDC.

As we reach the home stretch of the #DanIsAwake 40-hour experiment, here's a few fun facts about sleep.

• After 48 hours of no sleep, the body will start to "microsleep," where a person can doze off for a second or two with their eyes open.
• At 72 hours of no sleep, a person can start to hallucinate.
• Somnambulism is the scientific name for sleepwalking, and it is estimated to affect 4 percent of adults and 17 percent of kids.