PHILADELPHIA -- Nearly one out of five commercial truck drivers may be at risk for driving impairment because of poor sleep quality, the results of a study here suggested.
PHILADELPHIA, Aug. 15 -- Try to steer clear of that tailgating truck driver speeding down the interstate. He may be falling asleep.
That's the intuitive bottom line that emerged from a study of nearly 250 commercial truck drivers at high risk for sleep apnea and about 150 at low risk for the condition, identified by mailed questionnaires.
Nearly one out of five truck drivers may be at risk for driving impairment because of poor sleep quality, concluded Allan I. Pack, Ph.D., of the University of Pennsylvania School of Medicine here.
In the study, more than 13% of commercial truck drivers averaged less than five hours of sleep per night, and nearly 5% suffered from severe sleep apnea, reported Dr. Pack and colleagues said in the Aug. 15 issue of the American Journal of Respiratory and Critical Care Medicine.
Both conditions are associated with poorer performance on psychomotor vigilance and driving tests, and in some cases, the impairment is equivalent to being drunk, they said.
More than 90% of the drivers were men, and their average age was 45.
The researchers used motion detection devices worn on the wrist to measure how much sleep these drivers got per night at home over the course of one week. The drivers were then tested for sleep apnea with overnight, in-laboratory polysomnography and given a battery of neurobehavioral tests, including the Multiple Sleep Latency Test, the Psychomotor Vigilance Task, and the Divided Attention Driving Task.
While 28.7% of the drivers averaged seven to eight hours of sleep each night, 13.5% averaged less than five hours.
Slightly more than 28% suffered sleep apnea to some degree, and 4.7% had severe sleep apnea. Sleep apnea causes repeated awakenings during the night and reduces the quality of one's sleep.
Nearly half (49.5%) of the drivers who got less than five hours of sleep showed evidence of impairment on at least two of the three tests, compared with about 17% of drivers who got seven to eight hours sleep (P<0.0001).
Compared with drivers without sleep apnea, those with severe apnea were significantly more sleepy by objective measures (P=0.0002) and made significantly more errors on the driving test (P=0.001).
Of the 18.5% of truckers who were either sleep-deprived or suffered from severe sleep apnea, 29% had rates of attention lapses on the vigilance test comparable to those produced by alcohol intoxication, the researchers said.
Furthermore, 37% of these drivers committed rates of errors on the driving test that were also comparable to being drunk, the investigators said.
The investigators cautioned, however, that "the proportion of individuals with such performance impairments in our society is unknown, and there are no data that currently show an association between impairments in the tests we performed and crash risk in commercial drivers."
Another limitation of the study was that individuals were self-selected for the study based on response to questionnaires, so that sleepy individuals may have been more likely to respond, the authors said.
Nevertheless, "there are daytime neurobehavioral performance impairments that are found commonly in commercial drivers, and these are more likely among those with durations of average sleep less than five hours per night and those with severe obstructive sleep apnea," the authors concluded.
The Federal Motor Carrier Safety Administration, tasked with reducing crashes, injuries, and fatalities involving large trucks and buses, should employ strategies to identify sleep-impaired drivers by objective testing, treat those with severe sleep apnea, and promote to drivers the importance of getting enough sleep, the authors suggested.
According to the National Transportation Safety Board and other organizations that monitor traffic safety, fatigue is an "important factor" in serious crashes involving commercial vehicles, which kill about 5,600 Americans annually, the authors noted.