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Study at The Scripps Research Institute Indicates that Long-Haul Truckers Obtain Less Sleep than is Necessary for Alertness on the Job

September 11, 1997 - La Jolla, CA. - In the first study of its kind ever undertaken, a recent report by Merrill Mitler, Ph.D., of The Scripps Research Institute, and colleagues across the country provides scientific evidence that sleep deprivation in a sample of commercial, long-haul truck drivers was pervasive and led to drowsy driving, performance impairment and unintended lapses in attention. The greatest vulnerability to sleep or sleep-like states is in the late night and early morning hours.

The study, "The Sleep of Long-Haul Truck Drivers," by Merrill M. Mitler, Ph.D., James C. Miller, Ph.D., Jeffrey J. Lipsitz, M.D., James K. Walsh, Ph.D., and C. Dennis Wylie, appears as a special article in the September 11, 1997, edition of The New England Journal of Medicine. Based on results obtained from the Driver Fatigue and Alertness Study (DFAS), the largest and most comprehensive over-the-road study on driver fatigue and alertness in North America, it provides extensive information on the alertness, driving performance, and physiological and subjective states of commercial motor vehicle drivers as they perform real-time, revenue-generating trips.

The DFAS was initiated in 1989 by the Federal Highway Administration's Office of Motor Carriers in response to a Congressional directive contained in the Truck and Bus Safety and Regulatory Report Act of 1988 and conducted at a cost of $4.45 million.

According to William C. Dement, M.D., Ph.D., Professor of Psychiatry and Behavioral Sciences, Stanford University; and Chairman, National Commission on Sleep Disorders Research, "Recent studies comparing performance impairment caused by alcohol and sleep deprivation imply that our roads contain huge vehicles traveling at high rates of speed whose drivers are as impaired as those whose blood alcohol levels exceed the legal limit. With driver fatigue recently judged to be the number one problem in commercial transportation, we must begin to look at the impairment caused by sleep deprivation in the same light as that which is caused by alcohol consumption. This breakthrough study should be a wake-up call to the public as well as government officials who regulate the rules of the road."

The study consisted of 24-hour electrophysiologic and videotaped performance monitoring of 80 truck drivers who carried revenue-producing loads and were divided into four parallel groups of 20 drivers working five-day, 10-hour driving schedules in the United States or four-day, 13-hour schedules in Canada.

The results of the study indicate that, despite the opportunity to engage in longer periods of sleep, long-haul truck drivers obtained less sleep than is required for alertness on the job and that the greatest vulnerability to unwanted sleep or sleep-like states occurred during the late night and pre-dawn hours, a finding consistent with earlier published data and data on other industries.

According to Dr. Mitler, "The public needs to understand the forces at work that lead to this level of sleep deprivation, which in turn leads irrevocably to impairment and unintended lapses in attention. No amount of experience, conditioning, exercise, or diet will alter that sequence of events. Further, the effects of lost sleep are compounded over time; they do not lessen. By sleeping about two hours less per day than the estimated sleep needed during the course of the study, the drivers had accumulated at least a ten-hour sleep deficit by the last day. It is also known that too little sleep acts synergistically with circadian influences."

He continued, "It is important to recognize the deleterious synergistic effects of alcohol and other sedatives on alertness in the presence of sleep deprivation or medical conditions known to increase the tendency to fall asleep, such as sleep apnea. Our findings underscore the need to educate workers and schedulers about the importance of adequate sleep with respect to public safety."

Other research organizations participating in the study include Essex Corporation, Columbia, Maryland; Miller Ergonomics of Imperial Beach, California; Deaconess Hospital, St. Louis, Missouri; and the Sleep Disorders Centre of Metropolitan Toronto, Ontario.

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