Penn researchers examined 406 truck drivers and found those who routinely slept less than 5 hours a night were likely to fare poorly on tests designed to measure sleepiness, attention and reaction time and steering ability. Drivers with severe sleep apnea a condition in which someone stops breathing often during sleep also were sleepy and had performance impairment.
This study is among the largest and most comprehensive studies of truck drivers and fatigue ever done.
Pack: Tired Truck Drivers Drive Like Drunks
Allan Pack, MB, Ph.D., who headed the study, said the tired truck drivers had impaired performance similar to that of drivers who are legally drunk.
"We identified some very impaired people," said Pack, a sleep expert who directs Penn's Center for Sleep and Respiratory Neurobiology.
Nearly 5 percent of the truckers had severe sleep apnea and about 13 percent of the drivers got fewer than 5 hours of sleep a night on a regular basis.
"There are daytime neurobehavioral performance impairments that are found commonly in commercial drivers, and these are more likely among those who get an average of 5 or less hours of sleep a night and those who suffer from severe obstructive sleep apnea," the researchers concluded.
To measure the impact of fatigue on driver performance and safety, Penn researchers sent questionnaires to 4,826 truck drivers who had commercial licenses and lived within 50 miles of the Penn sleep centers. After getting complete responses from 1,329 drivers, researchers focused on 247 drivers at high risk for sleep apnea and 159 drivers at low risk.
28 Percent of Drivers Have Sleep Apnea
The truck drivers, almost all men and on average 45 years old, were given wrist motion detection devices to measure how much they slept during a week. In addition, they were monitored in the sleep lab while they slept to see if they had sleep apnea. About 28 percent of the drivers were found to have some degree of sleep apnea, with nearly 5 percent of them having a severe case.
Three tests then were given to measure daytime sleepiness and performance. The drivers were put in a dark room and observed to see how long it took them to doze off. Drivers who logged less than 5 hours of sleep dozed off more quickly than those who got 7 to 8 hours of sleep. Drivers with severe sleep apnea also dozed off more rapidly.
A lab test to analyze attention and reaction time and another to gauge "lane tracking ability" also turned up performance impairment among the sleep-deprived.
When the results were compiled, investigators discovered:
- Just over 5 percent of drivers showed impairment on all three performance-related tests.
- Nearly 60 percent did not fare well by at least one measure.
- About half of the drivers who got less than 5 hours of sleep had two or three impairments. That's compared to 10 percent of drivers who got more than 8 hours of sleep regularly.
- Likewise, about 60 percent of the drivers with severe sleep apnea had two or three impairments.
According to the study, about 5,600 people are killed each year in the United States in crashes involving commercial trucks. Many of the crashes happen when the driver falls asleep at the wheel.