Professional drivers who suffer from sleep apnea and subsequently become sleepy behind the wheel may pose grave safety concerns to our nation's highways.
According to the National Heart Lung and Blood Institute, obstructive sleep apnea (OSA) is a disorder that occurs when a person's airway collapses or is blocked while sleeping, which can lead to shallow breathing or pauses in breathing during sleep. The major predominant risk factor for OSA is obesity. As many as 40-50 percent of commercial drivers are obese, which means the prevalence of OSA among these drivers is considerably higher than in the general population, researchers said.
The researchers also pointed out that OSA is the most common medical cause of excessive daytime sleepiness (EDS) and is associated with a two- to seven-fold increase in the risk of motor vehicle crashes. The U.S. Department of Transportation asserts that an estimated 10-30 percent of large truck and bus crashes, which kill 5,000 and seriously injury more than 100,000 people each year, are linked to drowsy driving.
"Our goal is to develop objective screening methods beyond obesity for obstructive sleep apnea to be used in occupational health settings," said the study's senior author, Stefanos N. Kales, M.D., MPH, Division Chief and Medical Director of Employee and Industrial Medicine at Cambridge Health Alliance, where the study was conducted.
Psychomotor Vigilance Test
The researchers set out to determine whether the psychomotor vigilance test (PVT), a 10-minute test of attention, alertness and reaction time, could be used to screen and identify drivers at high risk for OSA/EDS. The test can be administered during a short office visit; requires only brief instruction; is performed on portable, hand-held computers; and can be easily and quickly read and interpreted.
In the study, 193 male commercial drivers and emergency responders undergoing occupational examinations took a 10-minute PVT and were instructed to achieve their fastest possible reaction times. Participants with discrete patterns of delayed reaction times were categorized as "microsleepers." The study identified 15 microsleepers, representing 8 percent of the study's participants.
The abnormal alertness and reaction time patterns detected by PVT were found almost exclusively among obese men whose body composition puts them at high risk for OSA. Moreover, the PVT seems to detect people likely to suffer from EDS based on other research, which has suggested that longer lapses in reaction time are highly likely to identify drivers experiencing eye closure, as opposed to simple distraction from the test. Eye closures while on task are consistent with microsleeps.
If the method and reaction time criteria are refined and validated in this setting, the PVT can be used to identify drivers needing urgent sleep evaluation before being qualified to continue as commercial drivers.
"This novel use of the PVT is extremely promising as a potential, 10-minute frontline check for sleepiness accomplished at professional drivers' federally mandated licensing exams, similar to vision and hearing screens common in current use," said Kales, who serves as an associate professor at both Harvard Medical School and Harvard School of Public Health.
The study was published online in the Journal of Occupational and Environmental Medicine.