The news that sleep may have played a role in New York's Metro-North train derailment is a terrible reminder that sleep isn't just a personal health issue -- it is also a matter of public safety, when it comes to the rest of people who we entrust with others' lives.
The engineer at the train's controls may have fallen sleep asleep in the moments before the train derailed. Officials with the National Transportation Safety Board have stated that the engineer had "sufficient time" to rest between shifts. We also have reports that the engineer had recently switched from an afternoon shift schedule to a morning schedule. This investigation is still underway, but given the details available at this point, there are several possible issues related to sleep that could be involved:
Highway hypnosis. There's very little scientific research devoted to this phenomenon, but it's a commonly reported experience among long-distance drivers: a trance-like state that comes over them during extended periods behind the wheel. In this dazed, semi-conscious state, vehicle operators report being awake and continuing to undertake tasks related to driving, but have limited memory of their actions and of time elapsing.
We don't know nearly enough about what triggers highway hypnosis or the full degree of impairment it may cause. One possibility is that this so-called state of hypnosis is actually a state of microsleep. Microsleep occurs when, under the influence of sleep deprivation, the brain shuts down activity in certain areas while other areas continue to function. This leads to a state of partial-wakefulness, a not-asleep-but-not-awake limbo that is similar to the hypnotized and trance-like demeanor that has been attributed to the Metro-North train engineer in the period leading up to the derailment. While this is a possibility, I think it is less probable, as the engineer never reports a memory loss. In fact, he reports that he remembers quite a bit up until the moments before he needed to slow the train down.
Sopite Syndrome. A form of motion sickness, this little known neurological disorder's primary symptoms are drowsiness and mood alterations caused by prolonged exposure to motion. People who suffer from Sopite Syndrome are especially prone to drowsiness in transportation settings. Symptoms can be exacerbated by sleep deprivation and sleep disorders, as well as by physical fatigue. There has been no motion sickness reported, and with a 10-year history as an engineer I think this would have already been noted.
Circadian rhythm problems. Sleep deprivation can occur from not having, or making, enough time for sufficient rest. It also can result from trying to sleep at the wrong times. The timing of circadian rhythms is innate, individual, and highly sensitive. We all fall somewhere on a continuum of night owl to lark, with different degrees of preference for activity and sleep in the evening hours or the early morning. This individual tendency toward activity or rest at certain times of the day is deeply ingrained. An individual whose circadian clock is wired to be active at night and at rest in the morning would have a difficult time falling asleep in the early evening and waking up before dawn -- even if given plenty of time off between work shifts to do so. I think this is the most likely scenario, given the information we have available.
Circadian rhythm problems also can arise as a result of unpredictable, irregular work schedules. Shift workers -- people who work varying schedules outside the traditional, 9-5 work week, are at significantly elevated risk for circadian rhythm disorders. Disruptions to normal circadian function can involve difficulty falling asleep, waking too early, and inconsistent sleep patterns. Circadian rhythm disorders are a cause of sleep deprivation, fatigue, and daytime sleepiness.
The sleep and health hazards associated with shift work are common among people who work in the transportation industry. These jobs, like many that involve public safety -- where being well rested, focused and alert is critical to performing job responsibly -- are also endeavors that pose particular hazards to sleep, frequently due to:
- Long hours
- Not enough down time between shifts
- Work schedules that change frequently, vary between day and night shifts, and require functioning at complex tasks in the early morning or late night
Shift work has well documented risks to sleep. People who work shifts are more likely to be sleep deprived, to experience lower quality sleep, and are at higher risk for sleep disorders, including obstructive sleep apnea and insomnia. They have greater difficulty maintaining regular sleep schedules. They are also at risk for the errors in judgment, problems with alertness, and difficulty focusing that come with sleep deprivation.
A 2012 National Sleep Foundation poll of transportation workers indicates that train operators report poor quality and insufficient sleep at significantly higher rates than both the general public and workers in other industries. Among train operators, 57 percent said they rarely or never received a good night's sleep, the highest level of dissatisfaction among the different types of transportation workers surveyed. They also report performance and safety issues related to sleep: More than 1 in 4 train operators said that sleepiness had affected their on-the-job performance one or more times per week, and 18 percent said drowsiness had led to a "near-miss" accident. The other transportation professionals -- including pilots, bus, taxi, and limousine drivers, as well as long-distance truck drivers -- report similar levels of sleep problems and safety concerns.
- Limiting shift duration (The National Sleep Foundation poll reports train workers now average 9.8-hour shifts, second only to pilots, at 10.4 hours)
- Extending time off between shifts
- Creating schedules that minimize rotating shifts that vary between day and night
- Screening personnel for sleep disorders
- Making sleep checks a regular part of re-certification and ongoing screening for job fitness
- Allowing naps during shifts
To these good suggestions, let me add this one: We ought to be providing drivers, pilots, and operators with skills and tools to manage sleep other than prescription sleep medication, including light therapy, CBT for sleep, and training in sleep hygiene.
These actions could all make a significant difference in improving sleep-related health and safety issues among transportation professionals. More broadly, we all need to participate in creating a fundamental shift in how we think about sleep and its role in safety and welfare in public transportation. It's not enough to know that an engineer fell asleep at the controls of the train. Arriving at a deeper understanding what caused the sleep episode is critical to preventing accidents like this one from happening again, and to making the transportation industry safer for all of us.
Michael J. Breus, PhD
The Sleep Doctor®
Everything you do, you do better with a good night's sleep™
Twitter: @thesleepdoctor @sleepdrteam
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