The Drowsy Driver

David Y. Huang, M.D., Tallahassee Pulmonary Clinic, P.A.
 

Introduction

Caribou Coffee's motto "Life is short, stay awake" summarizes the problem of drowsy driving car crashes. Drowsy is synonymous with sleepy, which simply means an inclination to fall asleep. Driver fatigue is usually equated with driver drowsiness. The National Sleep Foundation's annual Omnibus surveys consistently reveal that about 20% of Americans have, at some time, dozed off while driving. The National Highway Traffic Safety Administration estimates that 100,000 car crashes per year and at least 1500 deaths per year can be attributed to driver drowsiness. Drowsy driving crashes, or fall-asleep crashes, represent only 1-3% of police-reported car crashes. It is often very difficult to determine if driver drowsiness was the cause of a car crash, and currently there is no rapid objective test to measure driver drowsiness (like the Breathalyzer for alcohol level). Fall-asleep crashes are more common than is described in police statistics and actually represent 6-10% of self-reported car crashes. Some authorities believe that fall-asleep crashes are even more prevalent than this. Characteristics of fall-asleep crashes are listed in Table 1.

At Risk Drivers

Who is at risk for drowsy driving car crashes? Patients with obstructive sleep apnea (OSA), narcolepsy patients, night-shift workers, medical housestaff, commercial truck drivers, patients taking sedating medications, adolescents, and individuals suffering from acute or chronic sleep deprivation are all at risk for drowsy driving car crashes. Although OSA is perhaps the best-known cause of excessive drowsiness, sleep deprivation is actually the most common cause of driver drowsiness.

Obstructive Sleep Apnea

The three most important questions regarding OSA are the following:

1. Does OSA impair driving performance?
2. Do OSA patients have increased car crash rates?
3. Does treatment with nasal continuous positive airway pressure (CPAP) reduce car crash rates?

A Divided Attention Task test has been used to study the effect of alcohol and OSA on simulated driving performance.¹ Untreated OSA resulted in a tracking error that was equal to that caused by a blood alcohol level > 100 mg/dl. Steer Clear is another vigilance test that has been used to evaluate simulated driving performance.² Patients with untreated OSA had three times more driving errors (hitting obstacles) with Steer Clear than controls did. Thus, untreated OSA does impair driving performance. Since 80% of OSA patients remain undiagnosed in our country, a large number of impaired and drowsy OSA patients are driving on our roads. Obstructive sleep apnea patients also have a significantly higher risk of car crashes as summarized in Table 2.

Based on data from self-reported car crashes, nasal CPAP appears to significantly reduce car crash rates (Figures 1 and 2)^7,8 Therefore, OSA patients on CPAP therapy should be encouraged to wear their nasal CPAP for at least 6 hours each night to reduce the risk of "cardiovascular" morbidity and mortality as well as "vehicular" morbidity and mortality.
 

Narcolepsy

Untreated narcolepsy patients have pathologic sleepiness that impairs their driving performance² and very likely increases their risk of a drowsy driving car crash. Accurate data regarding car crash rates in narcolepsy patients are not available due to the rarity of this disorder (.03 - .06% prevalence). Unfortunately, up to 75% of narcolepsy patients remain undiagnosed.

Night-Shift Workers

Night-shift workers experience an increased number of health problems and poorer quality of life than individuals who do not perform shift work. Night-shift workers suffer from chronic sleep deprivation and are at a significantly increased risk of drowsy driving crashes at 7 am when they got off of their night shift.

Medical Housestaff

Medical housestaff are also at increased risk of driver drowsiness due to night-call duty and sleep deprivation. A one year survey of housestaff and faculty at Johns Hopkins University revealed startling information listed in Table 3.⁹ The p value for every category listed in Table 3 is < .001.

Commercial Truck Drivers

Commercial truck drivers are at increased risk of crashes, possibly up to two times higher than controls. Commercial truck drivers comprise 4% of all drivers but are involved in 17% of mortalities due to crashes. Truck drivers are more obese than the general population and may be more likely to have OSA resulting in excessive daytime drowsiness. Truck drivers may also be sleepier because they only get 5 hours of sleep a night. In the late night and early morning hours, some truck drivers have been documented to have microsleeps (20 seconds or longer of stage 1 sleep) based on continuous EEG testing while driving.¹⁰ The implications of driver drowsiness in the trucking industry are mind-boggling. The first lawsuit that claims a trucker was negligent in a crash due to self-imposed chronic sleep deprivation may set a precedent.

Patients on Sedating Medications

Patients on sedating medications are also at increased risk for excessive daytime drowsiness, but it is not clear if this automatically translates into a higher rate of car crashes. Sedating antihistamines (Benadryl), benzodiazepines (Ativan/Klonopin), narcotics (Hycodan), anticonvulsants (Tegretol), tricyclic antidepressants (Elavil), some SSRI's (Luvox), Trazodone, Remeron, and even some antihypertensives (Clonidine) can cause excessive drowsiness.

Adolescent Drivers

Adolescent drivers comprise 6-8% of all drivers but are involved in 16% of car crashes and 21% of automobile deaths. Adolescent males are at much higher risk for car crashes than females. Car crashes usually occur late at night (MN - 7 am). Alcohol is often involved. Speeding and inexperience are often quoted as the causative factors, and not wearing seat belts increases mortality rate. Driver fatigue or driver drowsiness due to sleep deprivation may play a very important role but has largely been ignored in the past. Physiologically, adolescents require 9-9¼ hours of sleep every night, but most high school students only get 7 hours of sleep a night.

Why Do People Have Drowsy Driving Crashes?

What is the role of driver drowsiness in car crashes? Jane Stutts from the University of North Carolina prepared a special report for the AAA Foundation for Traffic Safety in November 1999.¹¹ This was the first scientific case-controlled report to investigate the epidemiology of drowsy driving crashes and involved over 1400 drivers in North Carolina. There were 3 categories of drivers:

1. Drivers involved in a drowsy driving crash (drowsy crash drivers)
2. Drivers involved in all other crashes (control crash drivers)
3. Drivers renewing license (non-crash controls)

Driver drowsiness was perceived as the second most important factor in causing car crashes, with alcohol perceived as the most important factor. Night-shift work, chronic sleep deprivation, poor sleep, and sleep disorders were all associated with a significantly increased risk of a drowsy driving car crash when compared to controls. The Epworth Sleepiness Scale (ESS) is a common subjective assessment for excessive daytime sleepiness and was also evaluated in this report. An Epworth score of > 15, driving after midnight, and acute sleep deprivation (especially staying up for > 20 hours straight) were also associated with a significantly increased risk of a drowsy driving car crash.

Conclusions on Drowsy Driving Crashes and Sleep Deprivation

1. Drivers need to be educated that sleep deprivation increases drowsy driving crashes. In 1900 Americans got over 9 hours of sleep a night. Now Americans get an average of 7 hours of sleep a night. We should aim for at least 8 hours of sleep a night.
2. Drivers should be cautioned not to drive if drowsy or if markedly sleep-deprived since one night of sleep deprivation could be as dangerous as driving intoxicated.
3. High schools and driver education programs need to stress the importance of avoiding sleep deprivation in adolescents.
4. The "average driver next door" may be at increased risk for a drowsy driving crash because of sleep-deprivation due to long working hours and a new baby at home.

Legal Implications of The Sleepy Patient

Obstructive Sleep Apnea Patient

Mandatory categorical reporting of OSA requires that a physician report every patient with OSA to the Florida Department of Highway Safety and Motor Vehicles (DHSMV). The advantage of mandatory categorical reporting is that impaired patients are not allowed to drive. This protects the patient and society. The disadvantage of mandatory categorical reporting includes difficulty in precisely determining who is at risk for car crashes. Furthermore, some patients with OSA may avoid medical evaluation and treatment and others may seek disability if mandatory reporting of OSA is required. Most states do not advocate mandatory reporting of OSA. Florida has a permissive policy, based on the physician's discretion, for reporting a medical or mental condition that impairs driving ability.

American Thoracic Society Guideline: High Risk OSA Patient and Driving

The 1994 ATS Guidelines regarding sleep apnea and driving¹² recommended reporting "high-risk" OSA patients to the DHSMV when a patient met all 4 criteria:

1. Patient with OSA has severe daytime sleepiness
2. Patient has had a previous car crash or a near miss accident due to driver drowsiness or falling asleep at the wheel
3. Patient continues to drive
4. Patient refuses adequate treatment such as nasal CPAP or upper airway surgery

Most drivers who have OSA have not had car crashes and it is not reasonable to prevent all people with OSA from driving. Physicians should be given immunity from tort liability when they, in good faith, report appropriate drivers to DHSMV. A practical approach to OSA and driving is listed in Tables 4 and 5.

Reporting to Department of Highway Safety and Motor Vehicles

Reporting an impaired driver to the DHSMV is a very delicate situation. Most patients feel extremely threatened by this reporting act and some may even become belligerent. One must notify the patient that physicians are medically and ethically obligated to report to the DHSMV a condition that may impair a patient's driving ability. One could compare the OSA patient's condition to an epileptic patient who won't take his seizure medications and comment, "You wouldn't want him driving in your neighborhood until he got his seizures adequately treated, would you?" The patient should be informed that the DHSMV Medical Section determines if the medical condition is controlled and addresses the status of the patient's driver license. The patient should also be told that he may be able to safely drive sometime in the future, but only after further treatment and further evaluation indicates that his OSA is adequately treated. DHSMV Medical Reporting Form 72628 can be obtained from the Neil Kirkman Bldg, Room A227, Tallahassee, FL 32399-0500 or by Fax at 850-921-6147.

When is it Safe to Drive (or Fly)?

No objective test absolutely correlates with safe driving ability. One of the most difficult questions in the field of sleep medicine is "When is it safe for an OSA patient to drive (or fly)?

1. If Epworth sleepiness scale score is normal < 10?
2. If patient is compliant with appropriate level of CPAP? (uses it >6 hours qhs by timer)
3. If Multiple Sleep Latency Test (MSLT) is normal > 10 minutes?
4. If Maintenance of Wakefulness Test (MWT) is normal > 20 minutes?
5. If patient performs normally on "Driving Simulator" or "Divided Attention Task"?

The answer is not clear; but in Australia, you cannot be a commercial truck driver if you have OSA. In the United States, the screening, evaluation, and treatment of OSA in commercial truck drivers has not yet been mandated, but guidelines are currently in development. The Federal Aviation Administration may be the most avante garde organization. A pilot can fly only if OSA is adequately treated and an annual polysomnogram and Maintenance of Wakefulness Test (after surgery or with CPAP) are both normal. The above policies that apply to drowsy OSA patients can be used in the evaluation of other drowsy drivers as well.

Summary

Drowsy driving is a national health hazard

Major Factors

• Sleep deprivation, acute and chronic
• Alcohol/sedating medications
• Age: Adolescents
• Sex: Males
• Occupation: Commercial truck drivers, night-shift workers, and medical housestaff
• Diseases: OSA and other sleep disorders

Solutions

• Value sleep so we can get more sleep—8 hours or more each night
• Avoid driving after alcohol/sedating medications and avoid driving MN - 7 am
• Improve awareness regarding drowsy driving
• Legal and societal changes regarding driving regulations to improve driver safety
• Identify the drowsy driver, diagnose OSA, and appropriately counsel, refer, and treat the drowsy driver

References

1. George CF, Boudreau AC, Smiley A. Simulated driving performance in patients with obstructive sleep apnea. Am J Respir Crit Care Med 1996; 154:175-181.
2. Findley LJ, Unverzagt ME, Guchu R, et al. Vigilance and automobile accidents in patients with sleep apnea or narcolepsy. Chest 1995; 108:619-624.
3. Findley LJ, Unverzagt ME, Suratt PM. Automobile accidents involving patients with obstructive sleep apnea. Am Rev Respir Dis 1988: 138:337-340.
4. Teran-Santos J, Jimenez-Gomez A, Cordero-Guevara J. The association between sleep apnea and the risk of traffic accidents. N Engl J Med 1999; 340:848-851.
5. Young T, Blustein J, Finn L, Palti M. Sleep-disordered breathing and motor vehicle accidents in a population-based sample of employed adults. Sleep 1997; 20:608-613.
6. George CFP and Smiley A. Sleep apnea and automobile crashes. Sleep 1999; 22:790-795.
7. Cassel W, Ploch T, Becker C, et al. Risk of traffic accidents in patients with sleep-disordered breathing: reduction with nasal CPAP. Eur Respir J 1996; 9:2606-2611.
8. Krieger J, Meslier N, Lebrun T. Accidents in obstructive sleep apnea patients treated with nasal CPAP: a prospective study. Chest 1997; 112:1561-1566
9. Marcus CL and Loughlin GM. Effect of sleep deprivation on driving safety in housestaff. Sleep 1996; 19:763-766
10. Mitler MM, Miller JC, Lipsitz JJ, et al. The sleep of long-haul truck drivers. N Engl J Med 1997; 337:755-761.
11. Stutts JC, Wilkins JW, Vaughn BV. Why do people have drowsy driving crashes? Input from drivers who just did. AAA Foundation for Traffic Safety, Nov 1999. http://wwwaaafts.org/pdf/sleep.PDF
12. Official Statement of the American Thoracic Society. Sleep apnea, sleepiness, and driving risk. Am J Respir Crit Care Med 1994; 150:1463-1473.

Drowsy Driving Websites:

www.dcmsonline.org March, 2001/ Jacksonville Medicine