Sleep apnea and driving: the risk and how treatment helps

Untreated sleep apnea raises the risk of crashing, mostly because it leaves people sleepy behind the wheel. The good news is that treatment helps. Studies of people who started CPAP found their crash rates fell sharply, and daytime sleepiness often improves within days. If you have sleep apnea and use your treatment, you're in a much better position than someone who doesn't know they have it.

How big a problem is drowsy driving?

Drowsy driving is a real but hard-to-measure problem. NHTSA counted 644 deaths from drowsy-driving-related crashes in 2024. For 2017, it estimated 91,000 police-reported crashes involving drowsy drivers, about 50,000 injuries and nearly 800 deaths, and it says these numbers are likely an underestimate.

Counting is difficult because crash investigators can't always tell whether a driver was drowsy. NHTSA describes a pattern that drowsy-driving crashes tend to follow. They happen most often between midnight and 6 a.m. or in the late afternoon, when the body's internal clock dips. They often involve a single driver running off the road at high speed with no sign of braking, and they're common on rural roads and highways.

The American Thoracic Society estimates that sleepiness may account for up to 20% of crashes on monotonous roads, especially highways.

Is sleep apnea dangerous for drivers?

Untreated sleep apnea is dangerous for drivers because it raises crash risk. A 2009 meta-analysis concluded that people with obstructive sleep apnea are clearly at increased risk of a crash, with a crash-rate ratio likely between 1.21 and 4.89. The authors called untreated sleep apnea a significant contributor to motor vehicle crashes.

The American Thoracic Society describes obstructive sleep apnea as the most common medical disorder that causes excessive daytime sleepiness, and says it increases the risk of drowsy driving two to three times.

The reason is broken sleep. Cleveland Clinic lists excessive daytime sleepiness and microsleeps, brief moments of falling asleep during the day, among the complications of sleep apnea, and notes these are dangerous while driving. FMCSA makes a similar point for commercial drivers. It says undiagnosed or inadequately treated moderate to severe sleep apnea can cause unintended sleep episodes and problems with attention, concentration, awareness and memory.

The 2009 meta-analysis found that factors such as body mass index, AHI, oxygen levels and possibly daytime sleepiness may help predict which drivers with sleep apnea are more likely to crash. A large Swedish study, though, found that AHI on its own didn't identify the patients at risk. More on that below.

Who with sleep apnea is most at risk?

Drivers with sleep apnea seem most at risk when they are very sleepy, sleep very little or take sleep medicines. In a Swedish study of 1,478 people referred for sleep apnea, crash risk was 2.45 times higher than in the general population, and those factors were each linked with more crashes.

The Swedish researchers compared their patients' crash records with national traffic data. In the patients, these factors were linked with higher odds of a crash:

• severe daytime sleepiness, with an Epworth Sleepiness Scale score of 16 or more (about twice the odds)
• habitual sleep of 5 hours or less a night (about 2.7 times the odds)
• use of sleeping pills (about twice the odds)
• driving longer distances each year

The excess risk was most noticeable in people aged 65 to 80. Sleep apnea severity measured by AHI failed to identify the people at risk, which suggests that how sleepy you are matters more for driving than the number on your sleep study. Our guide to what AHI means explains that number, and waking up tired covers other reasons for daytime fatigue.

Does treatment lower the risk?

Treatment does appear to lower the risk. A 2010 meta-analysis pooled nine observational studies that compared crash rates before and after people with sleep apnea started CPAP. The risk ratio after treatment was 0.28, which works out to about a 72% drop in crash risk.

The same review found that daytime sleepiness improved significantly after a single night of CPAP, and performance in driving simulators improved within 2 to 7 days. There wasn't enough crash data to show exactly how quickly real-world risk falls.

The Swedish study points the same way. Among patients who used CPAP for at least 4 hours a night, the crash rate dropped from 7.6 to 2.5 crashes per 1,000 drivers a year.

These are observational studies, so they can't fully rule out other explanations, such as people who use CPAP also being more careful drivers. Still, guidelines take the evidence seriously. The American Thoracic Society makes a strong recommendation to treat confirmed sleep apnea with CPAP to reduce driving risk, based on moderate-quality evidence. It also recommends against relying on stimulant medicines to reduce driving risk, and suggests quick diagnosis and treatment for people at risk.

If CPAP isn't right for you, other treatments exist. Our overview of sleep apnea treatment options covers them, and your doctor can help you decide which fits.

What are the warning signs of drowsy driving?

The warning signs of drowsy driving include frequent yawning, trouble keeping your eyes open, not remembering the last few miles and drifting out of your lane, according to the American Academy of Sleep Medicine. NHTSA adds crossing roadway lines and hitting a rumble strip. Any of these means it's time to stop.

The AASM also says some common tricks don't work. Turning up the radio, opening the window and turning up the air conditioning are not effective ways to stay awake. Caffeine can raise alertness for a short time but isn't a substitute for sleep.

NHTSA warns that even with coffee, a seriously sleep-deprived driver can have microsleeps lasting four or five seconds. At 55 miles per hour, that's more than 100 yards traveled while asleep. Its advice if you get sleepy is to have one or two cups of coffee and pull over for a 20-minute nap somewhere safe, such as a lit rest stop.

The AASM says anyone who struggles to stay awake while driving even after adequate sleep should be evaluated by a doctor for a sleep disorder and treated when appropriate.

How can you drive more safely while you start treatment?

You can drive more safely while starting treatment by protecting your sleep and avoiding the times and habits that make drowsiness worse. NHTSA says getting enough sleep every day is the only true protection against drowsy driving, and experts urge seven to eight hours a night.

NHTSA's other advice applies to everyone, and it matters more if your sleep apnea isn't treated yet:

• Avoid alcohol before driving. It interacts with sleepiness to increase drowsiness and impairment.
• Check prescription and over-the-counter medicine labels for drowsiness, and use other transport where you can if a medicine makes you sleepy.
• Avoid driving during the peak sleepiness periods, midnight to 6 a.m. and late afternoon.
• If you must drive at those times, watch closely for warning signs, especially when driving alone.

It can also help to plan long trips with breaks and, where possible, to share the driving until your treatment has had a chance to work.

What should commercial drivers know?

Commercial drivers should know that FMCSA has no specific sleep apnea screening rule. Its regulations don't require medical examiners to screen drivers for sleep apnea or refer them for testing, and they don't set diagnostic or treatment requirements. Instead, FMCSA's 2024 Medical Examiner's Handbook gives examiners guidance.

Here's how FMCSA described that guidance when it published the handbook in January 2024:

• Using several risk factors together is a reasonable way to identify drivers at risk of moderate to severe sleep apnea, rather than relying on one factor alone.
• The examiner decides whether a driver needs to be screened, based on the driver's individual circumstances.
• The examiner also decides whether treatment is adequate or effective.
• The handbook states that untreated moderate to severe sleep apnea is associated with heart and blood vessel disease, metabolic disease and death.

FMCSA and the Federal Railroad Administration had considered a formal sleep apnea rule in 2016 but withdrew that proposal in 2017. The handbook still links to joint 2016 recommendations from FMCSA's Medical Review Board and its advisory committee on screening, diagnosing and certifying drivers with moderate to severe sleep apnea.

In practice, this means a driver with sleep apnea isn't automatically barred from commercial driving. If you drive for a living and have symptoms, getting tested and treated is the most direct way to protect yourself and keep driving. Bring records of your diagnosis and treatment use to your medical exam, and ask your sleep doctor what your examiner is likely to need.

What should you do if you think you have sleep apnea?

If you think you have sleep apnea, talk to a doctor and avoid driving when you feel drowsy in the meantime. The American Academy of Sleep Medicine lists snoring, choking or gasping during sleep, and daytime sleepiness among the warning signs, including trouble staying awake while driving. A sleep study, at home or in a lab, can confirm it.

Be honest with your doctor about sleepiness while driving, including any near misses. The American Thoracic Society encourages doctors to ask about driving risk and other causes of sleepiness, and to be familiar with the driving laws that apply where you live. Our list of sleep apnea warning signs and our guide to home sleep apnea tests can help you prepare. If snoring is your main worry, snoring vs sleep apnea explains how to tell the two apart.

Read next

• Is sleep apnea deadly? What the research says
• Sleep apnea treatment options
• Sleep apnea warning signs

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.