Could Your Sleep Habits Be Putting You At Risk Behind The Wheel?
You know that feeling when you get behind the wheel after a rough night of sleep and realize halfway through your commute that you're struggling to focus?
Maybe you turn the music up, crack a window, or reach for coffee and hope that does the trick. Sleepiness can affect driving in ways that are easy to underestimate, which is why researchers wanted to better understand whether our usual sleep habits might be connected to serious driving risks.
In a recent study of 482,507 adults, researchers looked at how much people typically slept and whether it was associated with their risk of dying in a motor vehicle accident.
About the study
Researchers followed these adults ages 20 and older who completed medical screenings between 1996 and 2017. Participants reported how long they typically slept, how well they slept, and whether they used sleeping pills.
The researchers then checked official death records to identify motor vehicle accident deaths and used statistical models to see how sleep duration was associated with that risk. They also accounted for other health and lifestyle factors that could influence the results.
There's already plenty of research connecting too little sleep with impaired alertness and driving accidents. This study looked more broadly at whether both sleep duration and sleep quality were associated with the risk of a fatal motor vehicle accident.
The safest sleep range fell somewhere in the middle
Most people in the study reported getting between 6 and 8 hours of sleep per night, a window that also comes up in research on sleep and healthy aging, and this group had the lowest risk of dying in a motor vehicle accident.
Compared with them, people who slept 4 to 6 hours had a 30% higher risk of dying in a motor vehicle accident. Those who slept more than 8 hours had a nearly identical 31% higher risk.
That created a U-shaped pattern, with risk increasing at both shorter and longer sleep durations. The association was even stronger among people who smoked, drank alcohol frequently, or used sleeping pills.
The findings don't mean that sleeping more than 8 hours makes you an unsafe driver. This was an observational study, so it can identify a relationship between sleep habits and crash deaths but cannot show that sleep duration itself caused those deaths.
Why sleep matters when you're driving
The connection between too little sleep and driving is fairly intuitive. When you're tired, your reaction time and attention can suffer, and sleep duration has been tied to long-term brain health as well.
Severe sleepiness can also cause you to briefly nod off, which is obviously a problem when you're moving at highway speed.
The longer-sleep connection is harder to explain.
Sleeping more than 8 hours could sometimes reflect poor-quality sleep or another health issue that leaves someone tired despite spending plenty of time in bed.
Sleep inertia, that groggy feeling after waking, may also temporarily affect alertness in the first stretch of the morning, before your brain fully bounces back. But these are possible explanations, not findings the researchers were able to confirm.
What to do before you hit the road
You can't control every factor that contributes to driving safety, but you can pay attention to how rested you are before getting behind the wheel.
- Aim for enough sleep: The lowest risk in this study was seen among people sleeping 6 to 8 hours, so getting roughly 7 to 8 hours most nights is a reasonable target for many adults.
- Don't push through serious sleepiness: If you're struggling to keep your eyes open or feeling unusually foggy, delay the drive, ask someone else to drive, or find another way to get there.
- Pay attention to persistent fatigue: If you regularly sleep more than 8 hours but still wake up exhausted, talk with your doctor. Poor-quality sleep or an underlying health issue could be contributing, and a few habit shifts can strengthen your sleep score.
- Take breaks on long drives: Regular stops can give you a chance to stretch, reset, and check in with how alert you actually feel.
The takeaway
A sleep schedule that consistently falls outside the 6-to-8-hour range was associated with a higher risk of fatal motor vehicle accidents in this large study.
While more research is needed to understand why, getting adequate, restorative sleep is one practical way to support alertness when it matters most.
