Somerville, MA...Obstructive sleep apnea (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. In a new study published online by the Journal of Occupational and Environmental Medicine, researchers from Harvard Medical School and Harvard School of Public Health investigated whether a recognized research tool, the psychomotor vigilance test (PVT), could be used as a novel screening tool to identify drivers at high risk for OSA/EDS.
The psychomotor vigilance test is a 10-minute test of attention, alertness, and reaction time (RT). The test, which can be accomplished within a short office visit, requires only brief instruction, is performed on portable, hand-held computers, and its output can be easily and quickly read and interpreted.
As the major predominant risk factor for OSA is obesity, the prevalence of OSA among commercial drivers (where as many as 40-50% are obese) is considerably higher than in the general population. Moreover, according to the U.S. Department of Transportation, large truck and bus crashes kill approximately 5,000 people and seriously injure over 100,000 individuals each year with an estimated 10-30% of these crashes 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, MD, MPH, Division Chief & Medical Director of Employee and Industrial Medicine at Cambridge Health Alliance, where the study was conducted. "Subjective reports of excessive daytime sleepiness are notoriously unreliable especially during fitness-for-work examinations, and obesity in isolation as a screen has generated resistance from many drivers."
In the study, commercial drivers and emergency responders undergoing occupational examinations took a 10-minute PVT and were instructed to achieve their fastest possible RTs. Participants with discrete patterns of delayed RTs were categorized as "microsleepers." The results revealed that among 193 male participants, 15 microsleepers (8%) were identified. Microsleepers were significantly more obese than other participants.
The abnormal alertness and RT 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.
"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," added Dr. Kales, who serves as an associate professor at both Harvard Medical School and Harvard School of Public Health. 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.
"Psychomotor Vigilance Testing of Professional Drivers in the Occupational Health Clinic: A Potential Objective Screen for Daytime Sleepiness," published by the Journal of Occupational and Environmental Medicine. Online publication before print. Authors: Chunbai Zhang, MD, MPH, Vasileia Varvarigou, MD, Philip D. Parks, MD, MPH, Shiva Gautam, PhD, Antonio Vela Bueno, MD, Atul Malhotra, MD, and Stefanos N. Kales, MD, MPH, FACOEM. The study was supported by the Federal Motor Carrier Safety Administration, a research award from the American College of Occupational and Environmental Medicine, and the National Institute for Occupational Safety and Health Education and Research Center.