The World Health Organization reported that in the United States, roughly 95,000 deaths in 1997 were attributed to unintentional injuries. The public health standpoint requires abandoning the notion that these injuries are unavoidable or fated, instead viewing them as predictable and preventable events, and examining the situations and circumstances in which detrimental consequences tend to arise from harmless intentions. Sometimes even the best intentions fail to bring about the stellar outcomes for which they were conceived, and unfortunately, even the most mundane of intentions can go awry with calamitous results. Why, for instance, is a plan to leave point A, hop into one’s automobile and then at sometime in the future, arrive at point B with both car and driver intact, all too often thwarted by a crash? Driving under the influence of alcohol is probably the most widely recognized cause of motor vehicle crashes, being cited as a factor in over one third of 41,611 fatalities in the U.S. in 1999. 1 Alcohol impairs the nervous system, affecting judgment, reaction time, and motor control thus seriously undermining the ability of mind and body to act as a smooth, integrated unit. A driver’s ability to perform as intended is also impaired by sleepiness. This issue has received increased attention in the last decade. Data from the National Highway Traffic Safety Association (NHTSA) indicate that driver drowsiness/fatigue is cited as a factor by the police in 56,000 crashes and 1550 fatalities annually .2 Whereas some drivers abstain from alcohol, none of us can resist the basic human need to shut down and replenish our reserves through sleep. Sleep is an episodic phase characterized by reduced awareness and responsiveness to both internal and external stimuli, and by motor inhibition. There is rarely a sharp and discernible transition from wakefulness to sleep. Instead, the transition occurs through a period of drowsiness or sleepiness, during which one assumes, though not necessarily simultaneously, the behavioral and physiological characteristics of sleep. Three main forces, namely, homeostatic drive, adaptive drive and circadian rhythm, contribute to the feeling of sleepiness. Homeostatic drive relates to the physiological need for sleep, and increases as time since previous sleep increases. Adaptive drive covers a range of mechanisms through which environmental factors influence the tendency to fall asleep. These include behavioral factors, such as physical or mental activity, and reflex factors related to sensory input, such as light, noise, or temperature. Finally, the circadian rhythm, or “internal clock” which governs physiological cycles such as hormone levels, is largely determined by genetics. Various factors including alcohol, certain medications and sleep disorders, may heighten these drives, thus increasing sleepiness. For the majority of the population, however, sleep restriction and fragmentation are the likely culprits. Sleep restriction may be acute, resulting from a single night of little or no sleep; or chronic, resulting from day after day of fewer than the optimal number of hours of sleep for the individual. In these cases, a “sleep debt” is incurred, which can only be honored by adequate sleep. Fragmentation occurs when sleep periods are interrupted, and may also decrease total sleep obtained. These interruptions are due primarily to behavioral and lifestyle circumstances, such as shift work, caring for an infant, or choosing to forgo sleep in favor of other activities. While the link to a fundamental biological need places all drivers at some risk for crashes due to sleepiness, certain populations are especially susceptible. Groups identified as being at highest risk are those with untreated sleep disorders, night or rotating shift workers, and young males, aged 16 - 29.2 In a 1991 survey of one thousand randomly selected Americans, five percent of chronic insomniacs reported having had an automobile accident due to sleepiness, versus two percent of occasional or non-insomniacs.3 Chronic insomnia occurs in approximately nine percent of the 280-million-strong U.S. population. 3 This means that the number of crashes that might be linked to insomnia alone is staggering. Also alarming are the results of a study comparing pediatric house staff on call every fourth night, who slept an average of 2.7 hours when on call (versus 7.2 when not on call), to faculty members who were rarely disturbed at night. In the sleep-deprived group, 49% reported having fallen asleep at the wheel, as opposed to 13% in the control group. 4 A vast majority (90%) of these incidents in the house staff had occurred post-call.4 This demonstrates the potentially life threatening consequences of habitual sleep deprivation in a real world setting. Measures can and are being taken to address this hazard from multiple standpoints. On an individual level, the best strategy is obviously to get adequate sleep before driving, and to avoid driving while drowsy. However, if it is too late for this, the best evidence to date supports two remedial measures to increase short term alertness: taking a fifteen to twenty minute nap, and consuming caffeine in the equivalent of two cups of coffee.2 Other common practices, such as opening the window, turning on the radio, or briefly exercising, though widely touted, may not be truly effective. In-vehicle monitors or alarms may alert drivers as they become too drowsy to continue safely operating the vehicle. The wisdom of installing such devices in passenger cars is nonetheless questionable, as they have the potential to promote a false sense of security. Viewing the effect of sleepiness on driving as a societal problem instead of merely a personal choice suggests interventions with the capacity to affect entire groups of people through environmental, institutional, or legal changes. For example, highways can be engineered to incorporate rumble strips. This relatively low cost effort has been reported to reduce off the road crashes by 30 to 50%.2 Other suggestions include employer management of shift scheduling, workplace education campaigns for shift workers, promoting awareness and treatment of sleep disorders, and graduated licensing programs that prevent new drivers from being on the road during the time period of highest risk, midnight to six A.M. 2 Various aspects of modern life can make it difficult for many to get a good night’s sleep. Use of strong artificial light at night coupled with low daytime light levels encountered due to television, atmospheric pollution, and spending a majority of time indoors, disrupt the natural circadian rhythms. Furthermore, the 24 hour society that began with electric lighting, the newer global economy, in which it is always daytime somewhere, and the booming cyberworld, which is unconstrained by the traditional boundaries of day and night, require many to abandon traditionally held sleep patterns. Obesity and obstructive sleep apneas have been linked to excessive daytime sleepiness.5 Urban noise may disrupt sleep at all hours, and urban sprawl may increase transit time required to get to and from work, leaving less time available for sleep. Even when it is possible for one to obtain adequate sleep, the perpetual availability of work, recreational, and social options often results in other options being chosen at the expense of sleep. Societal values tend to cement this decision. Sleeping is an activity for which no one receives awards or recognition. Worse, sleeping more than one’s peers can be viewed as a sign of weakness or laziness. Weakness, whether real or perceived, contrasts with our cultural admiration of youth, energy, and vitality, and laziness is not only undesirable, but may even be immoral—sloth, after all, is one of the seven deadly sins! This worship of activity and achievement joins with an increasingly marriage between our lives and our cars. In cities such as Atlanta that are hostile to the independent pedestrian, the combination of these factors can be deadly. Drowsy driving is an insidious hazard because it can’t be tested for as simply as alcohol, and may sneak up on a person and catch them unawares. Although it is usually illegal to cause damage or loss of life due to falling asleep while driving 5, unlike drunk driving, drowsy driving is something that we must practically leave up to self-regulation. If we decided to send police out on the roads to arrest all the tired people—well, at least it would completely resolve the intractable traffic problem for the lucky few who weren’t tired—yet. References 1. U.S. Department of Transportation National Highway Traffic Safety Association. Traffic Safety Facts: Overview. DOT HS 809 92, 1999. 2. Strohl KP, et al. Drowsy Driving and Automobile Crashes: NCSDR/NHTSA Expert Panel on Driver Fatigue and Sleepiness, http:\\www.nhtsa.gov/people/injury/drowsy_driving1/drowsy.html 3. Roth T, Ancoll-Israel S. Daytime consequences and correlates of insomnia in the United States: results of the 1991 National Sleep Foundation Survey II. Sleep 22 Sup 2:S354-8. 4. Marcus CL, Loughlin GM. Effect of sleep deprivation on driving safety in housestaff. Sleep 19:763-6. 5. Shneerson, John M. Handbook of Sleep Medicine. Blackwell Science, 2000.