People who work the night shift are at greater risk of getting into a drowsy-driving related car accident on the commute home due to the disruption of their sleep-wake cycles and lack of sleep, according to a new study at Brigham and Women’s Hospital (BWH).
For the study, researchers evaluated the daytime driving performance of night shift workers after a night of shift work compared to driving after a night of sleep. The findings show that 37.5 percent of drivers participating in a test drive after working the night shift were involved in a near-crash event.
When these same drivers had gotten a good night’s sleep, however, they had zero near-crashes. The findings show, for the first time, an increased risk of drowsy driving car accidents, as well as an increase in drowsiness (both self-reported and biological measures) when operating a real motor vehicle during the daytime following night shift work.
“Drowsy driving is a major-and preventable-public health hazard,” said Charles A. Czeisler, Ph.D., M.D., F.R.C.P., chief of the Division of Sleep and Circadian Disorders at BWH, and corresponding author of the study.
“These findings help to explain why night shift workers have so many more motor vehicle crashes than day workers, particularly during the commute home. Night shift workers should be advised of the hazards of drowsy driving and seek alternate forms of transportation after night shift work.”
In this study, 16 night shift workers participated in two sets of 2-hour driving sessions on a closed driving track at the Liberty Mutual Research Institute for Safety. Before one of the sessions, participants slept an average of 7.6 hours the previous night, with no night shift work. Before the other session, the same participants were tested after working a night shift.
The post-sleep and post-night shift drives occurred at approximately the same time of day for each participant.
Physiological measures of drowsiness were collected, including brief micro-sleep episodes as measured by an EEG, and partial eyelid closure with slow eye movements, which indicate the transition from wakefulness to sleep.
Driving performance was measured by the participants’ near-crash events, sessions terminated due to failure to maintain control of the vehicle, and weaving in and out of the lane.
Compared to the post-sleep drive, participants in the post-night shift drive showed increased driver drowsiness, deteriorating driving performance and increased risk of near-crashes. Over one third of the post night-shift drives required emergency braking maneuvers.
Almost half of the post-night shift drives were terminated early because the participants failed to maintain control of the vehicle. Post-night shift drivers showed increased drowsiness, impairment, and crash risk over the duration of the drive. Sleep-related impairment was evident within the first 15 minutes of driving.
The sleepy participants also had a significantly higher rate of lane excursions, longer blink duration and increased number of slow eye movements. The risk of micro-sleep episodes — sleeping for fewer than three seconds — increased after driving for more than 30 minutes.
“Even veteran night shift workers were vulnerable to the risks associated with drowsy driving, and exhibited reactions similar to behaviors observed in drivers with elevated blood alcohol concentrations,” said Michael L. Lee, Ph.D., lead author, and research fellow in the Division of Sleep and Circadian Disorders at BWH.
“A short commute for these drivers is shown to be potentially dangerous and the longer the drive, the greater the risk. Education about drowsy driving and its potential hazards could minimize this risk by prompting shift workers to eliminate or reduce the need to drive after night shift work, and to stop driving when their performance is impaired by drowsiness.”
The findings are published in the Proceedings of the National Academy of Sciences.
Source: Brigham and Women’s Hospital