The engineer at the the helm of the Metro-North train that derailed in December, killing four and injuring more than 70 people, suffers a major sleep disorder, according to the New York Times

A source told the Times that the National Transportation Safety Board (NTSB) will announce this week that William Rockefeller has a condition called sleep apnea, which was undiagnosed at the time of the crash. The Times explains that Rockefeller's condition was exacerbated by a recent shift to an earlier schedule: 

Sleep apnea involves pauses in breathing or shallow breaths, which can disrupt sleep and cause excessive daytime sleepiness, according to the National Institutes of Health. Mr. Rockefeller’s lawyer, Jeffrey P. Chartier, confirmed that his client had shared his medical records with investigators.

The Huffington Post reports that roughly 25 percent of American men, and 10 percent of women, have sleep apnea, but that as many as 80 percent of those with the disorder are undiagnosed — possibly because getting diagnosed means agreeing to a sleep study, which requires spending the night in a hospital hooked up to machines. Still, according to HuffPost, some industries require sleep apnea testing: 

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.

Despite the alleged diagnosis, no official ruling has made on the cause of the crash, and the engineer's condition has not been directly linked to the accident, as of yet. Last month, a report detailed concerning Metro-North security lapses. The Times reports that the safety board is expected to release more information from the most inquiry next week.