A truck driver steering 40 tons of steel down a busy interstate needs to stay alert on the job. That requires a good night's sleep. But a report in tomorrow's New England Journal of Medicine suggests that many drivers get far less sleep than they say they need. The finding suggests that many drivers may underestimate the effect of sleep deprivation on their driving ability. One implication, say the authors, is that despite existing recommendations that drivers take 8 hours between shifts, the trucking industry may need to allow more flexibility in sleeping and driving schedules.
Sleepy drivers can be as dangerous as drunk ones, and truckers--many of whom work long hours--are involved in accidents that injure 110,000 people and kill 5000 in the United States each year. To measure how much sleep truck drivers get during a typical week, a team led by Merrill Mitler of the Scripps Clinic and Research Institute in La Jolla, California, monitored the sleep patterns of 80 drivers for 5 days. The drivers spent their main sleep period in the lab, where researchers measured the length and type of sleep. While driving, their eye movements and brain wave patterns were recorded. The researchers also set up video cameras in the truckers' cabs, which recorded drivers' faces, the road ahead, and the truck's speed and road position. The researchers later sampled the videotapes for signs of sleepiness, such as drooping eyelids or a bobbing head.
The team found that drivers slept much less than their ideal. At the beginning of the study, drivers said they needed an average of just over 7 hours of sleep each day to stay alert. During the study, the average driver spent just over 5 hours in bed, and only 4.8 hours asleep. Although no participants were involved in accidents during the study, more than half had at least one drowsy spell while driving. Drivers on the graveyard shift slept less and suffered more drowsy spells than did their counterparts who drove during the day.
Most people aren't aware of the dangers of drowsy driving, say the authors. "Fatigue is a little like alcohol," says co-author James C. Miller. "You can't tell how impaired you are." Although sleep researcher David Dinges of the University of Pennsylvania School of Medicine cautions that sleeping in a laboratory may have changed the drivers' normal sleep patterns, he says the study--the first of its kind in 2 decades--will help trucking companies and regulators set safer guidelines for drivers' schedules.