Did you catch enough zzzs last night? The answer is probably no: Americans are notoriously short on sleep. For many, that’s just considered a fact of life, not something that could affect you on the road. But you might want to reconsider what factors to weigh before getting behind the wheel. As Ashley Halsey III reports for The Washington Post, new research suggests that skimping on even just a few hours of sleep greatly increases the risk of crashing.
According to a new report from the AAA Foundation for Traffic Safety, drivers who have gotten fewer than five hours of sleep in a 24 hour period have crash risks comparable with those who drive drunk. Researchers analyzed data from 4, 571 crashes that occurred between 2005 and 2007 recorded in the National Motor Vehicle Crash Causation Survey.
While conducting the survey, investigators looked into the circumstances behind each crash, from the roadway and vehicle to the drivers themselves. Each crash was severe enough that a car was towed from the scene and that emergency services were called.
Using that data, researchers analyzed the relationship between the amount of sleep reported by the drivers and their risk of being involved in a crash. They found that the less sleep a driver got, the more likely they were to crash. Unsurprisingly, those who got the least amount of sleep had the most risk. Compared to drivers who have slept for seven hours or more, those who logged four or fewer hours of sleep had 11.5 times the crash risk and those who reported four to five hours had 4.3 times the risk.
These numbers are comparable to people who consume alcohol before driving. In 2015, the National Highway Traffic Safety Administration, who also administered the crash causation survey, estimated that people who drive with blood alcohol concentrations of 0.15 (nearly twice the legal federal limit of 0.08) are roughly 12 times more likely to crash than those with legal blood alcohol concentrations.
But another facet of the findings is even more concerning: People didn’t have to run on a tiny amount of sleep to drive unsafely. Missing just an hour or two of sleep made a difference, too: Those who got between six and seven hours were 1.3 times more likely to crash, and those with five to six hours were 1.9 times more likely. Given the fact that one in three Americans doesn’t get seven hours of sleep a night, that equates to a lot of impaired drivers on the road.
The study did have limitations. Researchers couldn’t control for drug or alcohol use, and very few drivers studied self-reported getting fewer than five hours of sleep. The crash data also didn’t include accidents that occurred between midnight and 6 a.m.—hours when people could be the most sleep deprived.
Sleep deprivation is associated with other health risks, too, like a higher chance of chronic illness and even a shorter life expectancy. But the correlation between sleep deprivation and crashes could mean that sleeping too little and getting behind the wheel endangers other peoples’ lives, too. Food for thought before you pick up your keys: You might want to find your pillow instead.