Engineer Involved In Fatal Metro-North Train Derailment Had Undiagnosed Sleep Apnea

Train engineer William Rockefeller, who "zoned out" while at the controls of a Metro-North train in New York in December when it derailed, resulting in the deaths of four people and injuries of more than 70, had undiagnosed severe sleep apnea, according to news reports.

The New York Times reported that the sleep disorder -- which is characterized by pauses in breathing during sleep, which can lead to daytime fatigue -- was made worse by his recent change in shifts, to work in the early morning.

While sleep apnea affects at least one in four men and one in 10 women, most people with the condition -- as many as 80 percent -- are undiagnosed, according to the Cleveland Clinic.

Sleep apnea has been linked with a number of health ills -- including diabetes, obesity and heart disease -- and it also carries a huge financial cost. A 1999 study in the journal Sleep showed that untreated sleep apnea in the U.S. is associated with as much as $3.4 billion in additional medical costs.

Sleep apnea is notoriously dangerous for people in transportation-related industries in particular, since the condition causes daytime fatigue. Pilots, for instance, are required to undergo sleep apnea screening by the Federal Aviation Administration. And while truck driving rules from the U.S. Federal Motor Carrier Safety Administration don't address sleep apnea specifically, they do state that any condition that would impair ability to drive safely must be treated before the driver can regain "medically-qualified-to-drive" status.

Symptoms of sleep apnea are often not very specific, meaning not everyone who feels tired during the day or who snores at night has sleep apnea, notes the University of Maryland Medical Center. However, a doctor may recommend evaluation by a sleep specialist when sleepiness starts to affect quality of life or others' well-being/safety, or if someone has noticed pauses in breathing during sleep.

Sleep apnea diagnosis involves undergoing a sleep study, which includes a number of tests. The most popular test, a polysomnogram, involves the recording of heart rate, blood pressure, brain activity, eye movements, blood oxygen levels, air movement through the nose, snoring and chest movements during sleep. The National Heart, Lung, and Blood Institute notes that if a doctor suspects sleep apnea, he or she might try putting the patient on a CPAP machine (CPAP stands for continuous positive airway pressure, considered the gold standard treatment for sleep apnea), for half a night while the patient is undergoing a sleep study.