Sleep, science, and policy change.

Policies can be very difficult to change, and advocates of change who claim a logical or scientific foundation need valid, reliable, and convincing data. An example of the process is the policy of regulating truck drivers’ hours of service in order to reduce motor vehicle crashes. In 1935, Congress directed the Interstate Commerce Commission to establish hours-of-service rules for truckers. In 1938, despite a finding that no scientific basis had been provided, the commission established rules that limited driving to 10 hours in a 24-hour period and required a minimum of 8 consecutive offduty hours within 24 hours. Weekly driving was limited to 60 hours in seven days (or, alternatively, 70 hours in eight days). The agency also commissioned the first large study of fatigue among drivers, which, in 1941, showed a decline in performance on a battery of psychomotor tests during a period of 10 hours. However, the study did not link these results with the likelihood of motor vehicle accidents. 1 A decade later, McFarland and Moseley reported on the deterioration in the performance of one driver in a driving simulator during a 4-hour period after 24 hours of sleep deprivation. 2 They concluded that sleep is of great importance to drivers, but they observed that “little is known about sleep.” In the 1970s, studies of driver fatigue sponsored by the Department of Transportation found shortterm, cumulative, and diurnal effects occurring for work that was performed within existing hoursof-service limits. 3,4 However, the studies made no quantitative link between these data and the risk of accidents. The Department of Transportation proposed changes to the hours of service, but the recommendations were not implemented and the effort was dropped in 1981. As Mitler et al. reported, during the 1970s and 1980s the growth of research on sleep and the “biological clocks” that control it led to important discoveries about the many ways in which these processes influence human health and functioning. 5 In 1988, Congress directed the Department of Transportation to conduct additional research, and in 1989, a joint study of fatigue and alertness among drivers was begun that involved truckers in both the United States and Canada. In this study, my colleagues and I conducted round-the-clock monitoring of the electrophysiological results and performance of 80 truck drivers during more than 200,000 driver-miles. 6 In planning the study, we had a strong interest in measuring performance during substantially extended shifts but concluded that it would be too risky to carry out such an investigation on public highways. In the study that we conducted, drivers operated on public highways in compliance with hours-of-service rules, taking eight hours off duty daily. Even without extended shifts, we found that drivers slept less than was required for alertness on the job. 7 In 2003, the Department of Transportation increased required off-duty time from 8 hours to 10 hours in every 24-hour period. In this issue of the Journal , Barger et al. 8 address the issue of medical interns’ working extended shifts and the connection of those schedules with motor vehicle accidents. The authors report the results of their analysis of 1400 person-years of data collected from interns (2737 residents in their first postgraduate year), in which they found that the participants’ extended work shifts averaged 32.0± 3.7 hours and involved a mode of 2 to 3 hours of sleep. The odds ratio for reporting a motor vehicle crash after working an extended work shift was 2.3 (95 percent confidence interval, 1.6 to 3.3) and for reporting a near-miss incident was 5.9 (95 percent confidence interval, 5.4 to 6.3), as compared with the odds for the same person after working a nonextended shift. The monthly risk of a crash during the commute after an extended work shift was increased by 16.2 percent (95 percent confidence interval, 7.8 to 24.7 percent). In months in which interns worked five or more extended shifts, the risk that they would fall asleep while driving or while stopped in traffic was significantly increased (odds ratio, 2.39 [95 percent confidence interval, 2.31 to 2.46] and 3.69 [95 percent confidence interval, 3.60 to 3.77], respectively).