Shift Work Sleep Disorder Triples Risk of Car Accident, Study Says

People who suffer from shift work sleep disorder face the highest risk of a car crash, although sleep apnea and insomnia also heighten a person’s risk.

A new report is helping to quantify just how much sleep disorders can impact a person’s ability to drive safely.

The study, published in the journal Safety Science, found that drivers who suffer from shift work sleep disorder (SWSD) are nearly 3 times more likely to be involved in a car crash, compared with drivers without a sleep disorder.

As its name suggests, SWSD most often occurs in people who work nontraditional hours, such as the 11 p.m. to 7 a.m. shift. Working through the night and sleeping during the day over a long period of time can lead to a disorder in which a person has difficulty falling asleep when expected or needed. The Bureau of Labor Statistics found that, in 2017 and 2018, 16% of American workers worked a non-daytime schedule.

Existing research has already shown that sleep disorders can lead to unsafe driving; however, most of those studies were not based on real-world data, said co-author Praveen Edara, PhD, of the University of Missouri.

"In the past, researchers have studied sleep disorders primarily in a controlled environment, using test-tracks and driving simulators," Edara said in a statement. "Our study goes a step further by using actual observed crash and near-crash data from approximately 2,000 events occurring in six US states.”

The new study is based on the federal government’s second Strategic Highway Research Program. The investigators culled data from 1892 traffic events in 6 states, using random effect binary logistic regression models to estimate crash risk associated with SWSD, as well as sleep apnea and insomnia. They then accounted for confounding variables like roadway and traffic characteristics in order to come up with the contribution of sleep disorders to crash risk.

SWSD led to the highest crash risk, (odds ratio [OR] = 2.96); the risk was particularly high for older drivers (those aged 65 and older). Drivers with sleep apnea were 29% more likely to be in a crash or near-crash, and those with insomnia were 33% more likely to be in a crash or near-crash. The analysis also suggested that drivers with a sleep disorder are 29% more likely to be inattentive while driving.

Edara said he hopes that by quantifying and publicizing the risks associated with sleep disorders and driving, he and his colleagues can draw necessary research attention to the problem.

“We want to partner with public health and medical professionals whose expertise is sleep-related research to better understand why this is happening,” he said. “That will also allow us to explore what kind of countermeasures we can develop to test and improve the overall safety of these drivers and the other motorists around them.”

Edara said safety improvements can come from multiple directions. On one hand, improvements in the treatment of sleeping disorders can eliminate the cause of the increased risk, but he also noted that additional driving technologies, such as drowsy-driver alerts and even self-driving cars, could also mitigate risk. In addition, he said, it’s become easier for people to utilize ride-sharing apps and services, which could help those with sleep disorders avoid being behind the wheel altogether.


Bharadwaj N, Edara P, Sun C. Sleep disorders and risk of traffic crashes: A naturalistic driving study analysis. Safety Science. 2021;140:105295. doi:10.1016/j.ssci.2021.105295

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