Like HowStuffWorks on Facebook!

How Sleep Deprivation Works

Sleep Deprivation and Daytime Alertness
Sleep-deprived drivers are a very real road hazard.
Sleep-deprived drivers are a very real road hazard.
© matsilvan/iStock/Thinkstock

Sleep deprivation, no matter the cause, isn't healthy. No, you won't sleep when you're dead. You may get more accomplished on your to-do list when you're only catching a couple hours of sleep a night, but that comes with a price. More than one-third of people who don't get at least of seven hours of sleep at night report problems with daytime alertness. They have trouble concentrating, trouble remembering and recalling information and -- how terrifying is this -- trouble staying awake behind the wheel of their car. As many as 41 percent of U.S. drivers admit to having fallen asleep behind the wheel at least once, and about 4 percent admit they nodded off in the 30 days prior to being polled [source: AAA Foundation for Traffic Safety].

You might not notice some of the physiological things that come along with being sleep deprived, but you'll notice its impact on everyday tasks. Driving while drowsy is a dangerous mix -- as dangerous as driving while intoxicated, it turns out. The Exxon Valdez oil spill, for instance, is considered at least partly a fatigue-related tragedy. Drowsy drivers on the highways have impaired reaction time and alertness, decreased hand-eye coordination and poor judgment (including not knowing you're too fatigued to drive). And this is not just an issue for chronically tired drivers. Take the start of Daylight Saving Time, for instance: Americans setting their clocks ahead one hour for the start of Daylight Saving Time on the second Sunday in March coincides with a 17 percent increase in motor vehicle deaths on the following Monday [source: American Psychological Association]. And that's just one hour of lost sleep -- if you haven't slept in 17 to 19 hours, your drowsy driving is equivalent (or worse) than driving with a blood alcohol content (BAC) of 0.05 percent. Increase that to 24 hours or more without sleep -- or driving after sleeping 5 hours or less each night for a week -- and now we're talking about driving with the equivalent of a BAC of 0.1 percent. Add that up and you get about 1 million crashes, 500,000 injuries and 8,000 fatalities U.S. roads every year, all directly related to how little we sleep. Overall, it's estimated that sleep deprivation is the driving factor behind as many as one out of five car accidents [source: Williamson, Harvard Medical School].

And then there are the things sleep deprivation does to the body that you might not associate with your sleep debt, including an increased risk of developing chronic and serious health problems.