Sleep medicine has a role to play in educating the public about the dangers of drowsy driving.

Too bad it doesn’t exist anymore. We now live in a 24-hour society, and for most of us, less and less of those 24 hours is devoted to sleep. Sleep deprivation has become a way of life in the modern world, and its negative impacts on our lives are beginning to show, especially in our driving.

Chances are that even many sleep medicine professionals have experienced at least one of the following while behind the wheel:

• Missing a turn.
• Not seeing a speed zone change.
• Almost going through a red light.
• Thinking a piece of paper or other debris on the road was an animal.
• Wandering across the road’s center line or onto the shoulder.
• Not noticing a patrol car that had been following you.

If any of these things has happened to you while driving, you are not alone. These are all signs of drowsy driving, and according to the National Sleep Foundation (NSF), 60% of adult drivers have driven drowsy in the last year, and driver fatigue takes the blame for as many as 240,000 motor vehicle accidents in the United States annually.1 Researchers estimate that more than 1,500 deaths and 76,000 injuries each year can be directly attributed to drowsy drivers, at a cost of over $46 billion.2

Unsafe at Any Speed
Sleep is a biologic need with expected patterns of sleep and wake. Sleepiness results from the interruption of the normal sleep/wake cycle. Consistently restricting sleep by 1 or 2 hours a night can lead to chronic sleepiness. Sleeping is the only way to reduce sleepiness. Sleepiness can cause automobile accidents because it hampers performance and can eventually lead to the incapability to resist falling asleep at the wheel. Reaction time, awareness, attention, and the processing of information are all impaired in the sleep-deprived individual.

Currently, unlike with alcohol-related accidents, there is no measurable test that can be given in order to quantify levels of sleepiness at the crash site. Although existing understanding largely comes from inferential evidence, a typical crash related to sleepiness has the following characteristics:

• The problem occurs during late night/early morning or late afternoon.
• The crash is likely to be serious.
• The crash involves a single vehicle leaving the roadway.
• The crash occurs on a high-speed road.
• The driver does not attempt to avoid the crash.
• The driver is alone in the vehicle.3

Risk Factor 1: SLEEP LOSS
Many factors, including a current lack of knowledge about sleep, cause Americans to get insufficient rest either occasionally (acute sleepiness) or routinely (chronic sleepiness). Those who suffer chronic sleep restriction and sleepiness may also combine this lifestyle pattern with situational acute sleep loss, aggravating their risk of drowsy driving.

Chronic sleepiness. In a 1995 survey by the NSF, approximately one half of US adults reported experiencing sleeping difficulties sometimes, with about one in 10 saying their sleep problems were frequent. In 1997, when the NSF did a follow-up survey, three of four Americans who reported getting as much or more sleep than they thought they needed said that they were still sleepy during the day. When the survey administrators then tested the participants with the Epworth Sleepiness Scale (ESS), they found that one in three of the adult public scored as “significantly” sleepy and one in 20 scored at the “severe” sleepiness level.4

In a 1996 New York State survey, the reported frequency of drowsy driving in the past year was associated with the quantity and quality of sleep obtained. For example, those who reported having fair or poor sleep quality were more likely to have driven drowsy sometimes or very often than were those who said their sleep was good or excellent.4

Acute sleepiness. Even one night of poor sleep may cause extreme sleepiness. Short-term work demands, child care, socializing, and “pulling an all-nighter” are common causes of acute sleep loss.

Sleep-restrictive work patterns. Working varied or abnormal shifts is also a risk for both chronic and acute sleep deprivation. The New York State survey4 found that in nearly one half of automobile accidents the drivers reported having worked prior to the crash occurring. Also, a higher incidence of driving drowsy was associated with working a rotating shift, working a greater number of hours per week, and driving frequently for the job. Respondents also stated that working the evening shift led to sleepiness while driving. A majority of shift workers admit having slept involuntarily on the evening shift.

In addition, a study of hospital house staff working around the clock found higher levels of sleepiness and crashes following on-call periods. In a survey of hospital nurses, night nurses and rotating nurses were more likely than nurses on other shifts to report nodding off at work and at the wheel and having had a driving mishap on the way home from work.5

Both the time of day and the amount of time driving can be a risk factor. The highest proportion of drowsy-driving crashes occur during the late-night hours. Our natural circadian rhythm typically dictates that we sleep during darkness. Driving during this circadian peak in sleepiness can increase the risk for an automobile accident. Driving a large number of miles, driving a greater number of hours, and driving a greater number of hours without taking a break can also increase this risk.

We cannot always get 8 hours of quality sleep before driving. Therefore, we must plan ahead to reduce the risk of drowsy driving. Napping before a long drive can most certainly make up for short-term sleep loss and help maintain wakefulness during the drive. It goes without saying that you should avoid alcohol when driving, but especially when sleepy, due to its sedative effects. Not driving between the hours of midnight and 6 am, our “normal” sleep hours, can greatly reduce the chances of a drowsy driving accident.

When a driver becomes sleepy, the most obvious thing to do to avoid an accident would be to allow the driver an extended period of time to sleep. Sometimes, though, this is impossible. Studies have found two counteractive measures that can make a short-term difference:

Taking a nap. Even a short period of sleep before getting behind the wheel has been shown to greatly improve performance, even among chronically sleep-deprived people. This is not always possible, though, for several reasons. The driver might be unable to take short naps, rest areas may be unavailable, or someone driving alone might feel insecure stopping in a rest area at night.

Consuming caffeine. Even in low doses, caffeine greatly improves alertness in sleepy people. You can get the minimum dose needed in about two cups of coffee. Caffeine also is widely available in soft drinks and in tablet form. Driving simulators showed a reduced incidence of lane deviations, potential crashes, and drowsiness for about an hour after the consumption of caffeine.4

Some of the tricks that people have tried in the past, and more often than not still try, have proven to be completely ineffective. Such measures include: Getting out of the car and walking around, talking to other people, listening to the radio, and opening the car window. As stated earlier, there is basically no substitution for sleep.

One in five drivers admits to falling asleep at the wheel, and sleep-related accidents cost us an estimated $46 billion each year.2 With the demands that society has placed on us, and we have placed on ourselves, these numbers will surely rise. Education is the one tool we have at our disposal to help reverse the drowsy driving trend. As sleep medicine professionals, we must educate young drivers on the importance of getting enough sleep. We must educate shift workers on ways to improve their sleep hygiene and achieve adequate sleep. We must educate trucking companies on the dangers of 12- to 14-hour shifts behind the wheel. If significant changes are not made, we will long for the days when only 1,500 people died due to drowsy driving.

1. National Sleep Foundation. Drowsy facts and stats. Available at: Accessed January 16, 2006.

2. National Center on Sleep Disorders Research of the National Heart, Lung, and Blood Institute of the National Institutes of Health. Problem sleepiness in your patient. Available at: http: // prof/sleep/pslp_pat.pdf. Accessed January 16, 2006.

3. National Center on Sleep Disorders Research of the National Heart, Lung, and Blood Institute of the National Institutes of Health, the National Highway Traffic Safety Administration. Drowsy driving and automobile crashes. Available at: Accessed January 16, 2006.

4. McCartt AT, Ribner SA, Pack AI, Hammer MC. The scope and nature of the drowsy driving problem in New York state. Accident Analysis and Prevention 1996;28:511-17.

5. National Highway Traffic Safety Administration. The road to preventing drowsy driving among shift workers employer administrator’s guide. Available at: Accessed January 16, 2006.