Commentary: Get safe … get sleep!

Article Outline

• References
• Copyright

Ah sleep! What a beautiful thing, and never in my life have I found it as precious as I do now as a husband and father, clinical researcher, and academic emergency physician. Not surprising, and whether you're a medical student, emergency medicine resident, or a practicing emergency physician, I am sure that most of you reading this contribution to NHTSA Notes would have the very same and equally poignant sentiment. However, from a traffic safety perspective, what it comes down to is we are not getting enough of it, and it has major safety implications for every one of us on the road, especially us shift workers.

The National Sleep Foundation estimates that nearly 50 million Americans are not getting the minimum amount of sleep necessary to keep them alert and functional the next day. Moreover, 2 in 5 people experience enough daytime sleepiness to have it interfere with their activities several days a month, and 1 in 5 have this level of sleepiness several days a week.¹ Put these findings into the context of the driving public and commercial vehicle operators and it's easy to understand how drowsy driving can be a causal factor in an estimated 100,000 crashes, 40,000 nonfatal injuries, and 1,550 fatalities each year.

Although drowsy driving may seem like a comparatively benign event with seemingly simple remedies, the National Highway Traffic Safety Administration (NHTSA) has long recognized this as a significant and complex public health threat. For over a decade, the agency has worked diligently to understand the many intricacies of drowsy driving. Validating measurements of loss of alertness while driving, exploring the development of effective technological countermeasures and testing them in “real world” driving environments, and trying to better understand the perceptions and demographics of individuals at risk for drowsy driving are but a few of the areas the agency has addressed.

Early on, NHTSA recognized the need to find a reliable and accurate method of measuring drowsiness. In the mid to late 1990s, several biobehavioral monitors aimed at identifying sleepy drivers became available. However, traffic safety and sleep science experts alike became concerned that few had been rigorously evaluated and that this could lead to the continued development and propagation of dangerously ineffective devices.

Knowing that drowsiness could be easily observed and its effect measured by psychophysiologic changes and psychomotor performance decline, NHTSA set out to study different technologies. The hope was that a reliable metric could be validated, worked into an automated computer-based algorithm, and ultimately integrated into an unobtrusive “in-vehicle” technology that would accurately measure drowsiness.² What the agency found was that actual drowsiness could be reliably captured by measuring the percentage of eyelid closure in study subjects. Better known as the “PERCLOS” metric (PERcent CLOSure of eyelid), this was developed by Wierwille and Ellsworth³ and measures the proportion of time that a subject's eyes are closed during a 1-minute period as judged by a trained observer. Moreover, PERCLOS focuses on slow eyelid closures rather than blinks, with slow closures interpreted as a physiologic indicator of drowsiness and interruption of visual information gathering.³ With this drowsiness metric validated and integrated into a small unobtrusive camera mounted in vehicles, NHTSA commenced its in-field testing several years ago. With the emission of a noninterfering low-level infrared light directed at the driver's eye, the drowsiness detection device captures eyelid closures. Once the number of closures exceeds a predetermined threshold, the driver is alerted by both audio and visual warnings. At the same time, the driver is informed as to the length of his longest lapse of attention in the previous measurement interval and the distance the vehicle traveled during that lapse. All of this encourages the driver to take appropriate and prompt mitigating action.

Currently, the in-field testing encompasses real-time data gathering from 45 instrumented commercial trucks that have collectively traveled several hundred thousand miles and provided data in the magnitude of several terabytes. Completion of this in-field study is estimated to occur by late 2005. Data analysis from this study will provide some of the first in-depth systematic evaluation of “real world” drowsy driving events and the performance of the PERCLOS-based in-vehicle safety device. The information gathered will be used to inform and refine methodologies for future passenger vehicle studies in order to eventually incorporate these safety technologies into new vehicles.

While the technological race in this area of traffic safety goes on, work has continued to achieve a greater understanding of the makeup of drowsy driver crashes and insight into beliefs and perceptions held by drowsy drivers. In 1997, NHTSA convened an expert panel in collaboration with the National Center on Sleep Disorders Research and the National Heart, Lung, and Blood Institute.⁴ The purpose of the collaborative effort was to provide a summary of existing and ongoing research coupled with expert opinion in the area of driver fatigue and sleepiness. This information would be used to provide a research priority list, as well as to provide key information for future drowsy driver educational campaigns. Summary statements put forth by this expert panel highlighted: (1) characteristics of drowsy driver crashes (eg, serious single-vehicle crash, occurring in the late night, early morning, or midafternoon; no evidence of avoidance maneuver before crash; crash on a high-speed road); (2) associated risks for drowsy driving crashes (eg, sleep loss, driving for extended periods of time without a break, use of sedative medications, use of alcohol coupled with sleep loss, the presence of an undiagnosed sleep disorder); and (3) populations at highest risk for these types of collisions (eg, drivers aged 16 to 29 years, men, shift workers, individuals with sleep apnea syndrome or narcolepsy). The expert panel recommended countermeasures focused on encouraging drivers to plan to get sufficient sleep; not consuming alcohol, particularly when sleep has been inadequate; limiting driving between midnight and 6 am; and educating high-risk groups, health care providers, and policymakers.

Although collaborating experts and the agency recognized the urgency to disseminate educational materials to “at-risk” groups, further qualitative research by the Harvard School of Public Health in conjunction with NHTSA found that certain groups, such as shift workers, were more motivated to change their behavior to avoid drowsy driving events.⁵ Focus group study outcomes of 2 study groups, young men and shift workers, unveiled several insightful findings that would influence drowsy driver campaign messages. In general, it was evident that both study groups suffered from chronic sleep deprivation (sounds familiar), and this was supported overwhelmingly by self-reports of first-hand experiences of drowsy driving events. Although the study groups understood the extent of the drowsy driving problem to varying degrees, neither group felt efficacious or confident enough to optimize their sleep hygiene. Furthermore, both groups thought that the pressures of school, work, family, and other responsibilities (sometimes social activities) frequently put them in drowsy driving situations. Finally, it was found that in order to develop a safety message that would appeal to these groups, the message should incorporate the relevance of family and significant others, lifestyle choices that included better sleep hygiene, and thoughtful planning before road travel including sufficient sleep prior to embarking on a lengthy trip. The study groups also thought these messages would be best received in a news magazine television program format. The shift workers studied encouraged providing similar information for other shift workers in both video and print formats.

Although the focus group study provided essential information regarding beliefs and perceptions of drowsy driving by those most at risk, only recently has the prevalence of this problem become better defined. In the spring of 2002, the Gallup Organization and NHTSA teamed up to survey more than 4,000 drivers nationally on the nature and scope of distracted and drowsy driving.⁶ Because drowsy driving has been generally accepted to be profoundly underreported in police crash reports, this survey provided national prevalence estimates of this problem. Thirty-seven percent of those drivers surveyed reported that they have nodded off while driving at some point in their lives, and nearly 30% of these said that their last drowsy driving event had happened in the past year. Furthermore, 10% of drowsy drivers said that their most recent event had occurred in the past month. This 10% of drowsy drivers represents an estimated 7.5 million drivers who have experienced a drowsy event behind the wheel in the previous month. That's a lot of drowsy drivers!

Additionally, data from this self-reported survey show that more than one third of drowsy driving events occur between the hours of 6 am and 5 pm and among drivers who have been behind the wheel for 1 hour or less. If these findings are not enough evidence to legitimize the continued pursuit of effective drowsy driving countermeasures, consider the following: of those who reported they nodded off while driving in the previous 6 months, 33% ended up wandering into another lane or onto the shoulder of the road, and 19% found they had crossed the center line when they awakened from their drowsy event.

The public health threat is clear, yet the most effective intervention strategy beyond recommending sleep is yet to be found. However, the following points are items we should all consider for ourselves and convey to our friends, family, and patients in order to protect everyone from an unexpected visit to our neighborhood trauma center:

If you want to stay safe on the road, get enough sleep.

Back to Article Outline

References 

1. National Sleep Foundation. 2002 Sleep in America Poll [National Sleep Foundation Web site]. Available at: http://www.sleepfoundation.org/img/2002SleepInAmericaPoll.pdf. Accessed June 6, 2005.
   • View In Article
2. US Department of Transportation, National Highway Traffic Safety Administration . Evaluation of Techniques for Ocular Measurement as an Index of Fatigue and the Basis for Alertness Management. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration; April 1998;DOT HS 808 752
   • View In Article
3. Wierwille WW, Ellsworth LA. Evaluation of driver drowsiness by trained raters. Accid Anal Prev. 1994;26:571–581
   • View In Article
   • MEDLINE
   • CrossRef
4. US Department of Transportation, National Highway Traffic Safety Administration, National Center on Sleep Disorders Research, National Heart Lung and Blood Institute. Drowsy driving and automobile crashes [National Highway Traffic Safety Administration Web site]. Available at: http://www.nhtsa.gov/people/injury/drowsy_driving1/Drowsy.html. Accessed June 6, 2005.
   • View In Article
5. Nelson T, Isaac NE, Graham JD. Development and testing of countermeasures for fatigue related highway crashes: focus group discussions with young males, shift workers, and shift work supervisors [US Department of Transportation, National Highway Traffic Safety Administration Web site]. Available at: http://www.nhtsa.dot.gov/people/injury/drowsy_driving1/listening/title.htm#title. Accessed January 6, 2005.
   • View In Article
6. The Gallup Organization. National survey of distracted and drowsy driving attitudes and behaviors: 2002 [US Department of Transportation, National Highway Traffic Safety Administration Web site]. Available at: http://www.nhtsa.dot.gov/people/injury/drowsy_driving1/survey-distractive03/index.htm. Accessed January 5, 2005.
   • View In Article