How Sleep Deprivation Affects Your Ability to Drive

by Martin Reed Patient Advocate

The American Academy of Sleep Medicine (AASM) considers drowsy driving to be a serious public health concern. A policy statement issued by the association claims that driving while sleep deprived can have the same consequences as driving under the influence of drugs or alcohol.

How serious is the problem?

According to the AASM, 328,000 crashes annually in the U.S. can be blamed on drowsy driving, including 6,400 fatal crashes — and those aged between 16 and 24 are most at risk.

A 2014 study conducted by the AAA Foundation for Traffic Safety found that 21 percent of all crashes in which a person was killed involved a drowsy driver.

Why does sleep affect our ability to drive?

When we are drowsy, we are less alert and attentive. As a result, reaction times and decision-making skills suffer.

Making the risk even greater is the fact that drowsy driving can be hard to identify; the AASM revealed that some drivers weren't even aware they had fallen asleep at the wheel, even if they were asleep for a few minutes.

Is a specific driving skill affected?

A 2016 European study published in Biological Psychology set out to determine how sleep deprivation affects driving performance.

Researchers recruited 16 healthy male and female volunteers. Each participant:

  • Possessed a valid driving license for at least four years

  • Averaged at least 5,000 kilometers (3,100 miles) of driving experience per year

  • Had a body mass index of between 19 and 29

  • Enjoyed good sleep quality as measured by the Pittsburg Sleep Quality Index

  • Was required to abstain from drug or alcohol abuse, smoking, and excessive caffeine consumption (defined as six or more cups of coffee per day)

Participants were not permitted to be a part of the study if they:

  • Were shift workers

  • Had a history of a sleep disorder

  • Were extreme morning or evening types

  • Had any history of psychiatric or medical illness

  • Were abusing alcohol (or had a history of doing so)

  • Were using psychoactive medication

Each participant drove 100 kilometers (60 miles) on a highway, accompanied by a licensed driving instructor. Participants were tasked with maintaining a constant speed and a steady position in their driving lane, except when passing slower vehicles.

Participants followed the routine once after a night of normal sleep, and once after a night of total sleep deprivation.

Researchers found that compared to drivers who had enjoyed a night of normal sleep, sleep deprived drivers were significantly less capable of maintaining their driving trajectory. In other words, sleep deprived drivers weaved on the road more than drivers who had slept well.

Interestingly, the study found that when drivers approached the halfway point and the endpoint of the driving task, they weaved less. As the authors of the study pointed out, this may suggest that even a short break during driving could improve driving performance.

It's worth noting that seven of the sleep-deprivation driving tests were terminated prematurely. In one case, the driving instructor judged the participant to be too drowsy to safely continue driving. In the remaining cases, participants themselves felt too drowsy to continue driving in a safe manner.

Pay attention to the warning signs

As it's possible to fall asleep at the wheel for short periods of time without realizing it, it's good to be aware of the symptoms of drowsy driving. These include:

  • Frequent yawning

  • Drifting out of your lane

  • Missing road turns or signs

  • Difficulty maintaining your speed

  • Difficulty keeping your eyes open

  • Inability to remember driving the last few miles

If you notice any of these symptoms, it's important to pull over and rest. As the 2016 study suggested, even a small break can be helpful.

In fact, an expert panel assembled by the National Center on Sleep Disorders Research and the National Highway Traffic Safety Administration suggested that a nap of just 15 to 20 minutes can make a short-term difference in driving alertness.

Make sure that if you are planning a long journey, you get enough sleep beforehand. It can also be helpful to share the driving with other passengers if they are feeling more alert than you.

Make sleep a priority

Sleep quality is important throughout our lives; not just before a car journey! If you are living with sleep issues, don't ignore them — seek help and you could improve many more aspects of your life, including your overall health.

Martin is the creator of Insomnia Land’s free insomnia sleep training for adults. His online course uses CBT techniques to teach participants how to fall asleep without relying on sleeping pills. More than 4,000 insomniacs have completed his course and 97 percent of graduates say they would recommend it to a friend.

Martin Reed
Meet Our Writer
Martin Reed

Martin is the creator of Insomnia Coach, an eight-week course that combines online sleep education with individual sleep coaching. His course helps clients improve their sleep so they can enjoy a better life with more energy and start each day feeling happy, healthy, rested, and refreshed. Martin also runs a free sleep training course that has helped over 5,000 insomniacs. He holds a master’s degree in health and wellness education and studied clinical sleep health at the University of Delaware.