Sleep-Deprived People Are More Likely To Be In Car Crashes, Research Says

Sleep deprivation is linked with a higher likelihood of being in (and being responsible for) a car crash, says a new study. These risks may increase when sleep deprivation is more severe.

The study, which was published in the journal SLEEP, found that people who slept for fewer than seven hours within the past 24 hours have a greater chance of being in and being responsible for car crashes. People who slept for fewer than four hours within the past 24 hours demonstrated an even higher likelihood of being culpable for a crash.

This study adds to a growing body of research that explores the relationship between sleep deprivation and unsafe driving. It comes on the heels of a AAA Foundation for Traffic Study report, which found that drowsy driving plays a role in 9.5 percent of all car crashes.

This latest study is the first peer-reviewed study to quantify a driver’s risk of being responsible for a crash relative to how much they slept the night before.

Man driving carASDF_MEDIA/Shutterstock

Car Crash Culpability Increases With Sleep Deprivation

The study looked at U.S. Department of Transportation data pertaining to 6,845 drivers who were involved in a representative sample of car crashes between 2005 and 2007.

In order to create a type of control, the researchers compared data between drivers who were deemed culpable for a given crash relative to drivers who were nonculpable. They also controlled for driver-related, fatigue-related, and environmental factors and considered the specific errors that contributed to each crash.

After conducting this analysis, the study’s authors observed that:

  • Drivers who reported having slept for only six, five, or four hours in the 24 hours prior to a crash were 1.3, 1.9, and 2.9 times more likely, respectively, to be responsible for car crashes compared to drivers who reported getting seven to nine hours of sleep in the same time period.
  • Drivers who reported having slept less than four hours in the 24 hours prior to the crash were 15.1 times more likely than well-rested drivers to be responsible for car crashes. This crash risk is similar to the risk of someone with a blood alcohol concentration of approximately 1.5 times the legal limit.
  • Drivers who slept for less than four hours were also at a higher risk of single-vehicle crashes overall and were 3.4 times more likely to be responsible for a single-vehicle crash. Statistics suggest that single-vehicle crashes tend to be more deadly than multi-vehicle crashes.
  • The chances of being responsible for a car crash increased slightly when a range of factors were present, including a recent change in a person’s sleep schedule, feeling tired upon waking, and driving for three or more hours at a time.

RELATED: Where You’re Most Likely To Be Killed By A Drowsy Driver

Drowsy driverSupaleka_P/Shutterstock

Drowsy Driving On The Rise

Conventional medical wisdom holds that adults should sleep for seven to nine hours each night in order to feel well-rested. But research consistently finds that many Americans sleep less than that on a regular basis.

This helps explain why drowsy driving is pervasive in the U.S. The AAA study cited above suggests that drowsy driving may play a role in eight times as many crashes as original estimates thought.

Drowsy driving occurs whenever a person feels tired, sleepy, or exhausted while driving. It can result in several negative consequences on the road, including impaired reaction time, diminished judgement abilities, an increase in aggressive behavior, and falling asleep at the wheel.

Even if a tired driver doesn’t fall asleep while driving, they’re still a threat on the roadways.

“Falling asleep isn’t the only risk,” Tefft told ScienceDaily. “Even if they manage to stay awake, sleep-deprived drivers are still at increased risk of making mistakes — like failing to notice something important, or misjudging a gap in traffic — which can have tragic consequences.”

[Editor’s Note: The content provided on this site is for general informational purposes only. Any information provided is not a substitute for professional medical advice. We encourage you to consult with the appropriate health expert if you have concerns.]

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Laura Newcomer

Laura Newcomer is the Editorial Controller at Mattress Clarity, where she occasionally writes sleep news. She's worked as a professional writer and editor for over a decade and has been published in or on outlets such as TIME, Washington Post, Inc., Entrepreneur, Huffington Post, Women's Health, and many more. Her primary areas of interest include sleep, fitness, nutrition, eco-friendly living, education, and all things wellness.

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