Felix Lam/for New York Daily News
Rescue workers help passengers who had been on the Metro-North train when it derailed near the Spuyten Duyvil station in the Bronx.
Sleep apnea may have caused the locomotive engineer in the deadly Metro-North crash to zone out just before the train tumbled off the tracks.
William Rockefeller is expected to undergo an evaluation for the sleep disorder, a process that requires overnight monitoring, a source told the Daily News on Thursday.
Sleep apnea causes sufferers to stop breathing repeatedly while they are snoozing — leaving them exhausted when they finally wake up.
They often don’t realize they have it, the American Sleep Apnea Association said.
It is a “debilitating and life-shortening ailment that’s estimated to affect 22 million Americans,” according to the group. “Untreated, it can lead to depression, heart disease, diabetes and fatal car crashes.”
Portly people like Rockefeller are more prone to suffer from sleep apnea, experts said.
It has become such a problem that the Federal Aviation Administration recently announced a plan to screen overweight and obese pilots for the condition — and ground those who have it until they are treated by a sleep expert.
Rockefeller, 46 of Germantown, N.Y., is on unpaid leave and has stayed out of sight since the Sunday morning crash in the Bronx, which left four passengers dead and 75 more injured.
His lawyer, Jeffrey Chartier, did not return a call for comment.
A wake was held for Donna Smith, who died in Sunday’s Metro-North train derailment.
But immediately after the wreck, Rockefeller told cops, “I was in a daze,” The News reported on Tuesday.
That was followed by claims from a honcho in Rockefeller’s union who said he “basically nodded” just before the train — barreling down the tracks at 82 mph — derailed on a treacherous curve north of the Spuyten Duyvil station.
Anthony Bottalico, director of the Association of Commuter Rail Employees, also insisted that Rockefeller was not sleep-deprived.
The National Transportation Safety Board, which is investigating the catastrophe, agreed that Rockefeller had plenty time to recharge his batteries. But the feds declined to comment on Bottalico’s claim that Rockefeller zoned out at the controls.
Meanwhile, the MTA has admitted that Rockefeller’s train was equipped with an “alerter” system designed to rouse a dozing driver. But it was in the locomotive, which was pushing the train down the tracks from the back.
Rockefeller was operating the train from the first car when it headed into a treacherous curve where trains are supposed to slow down from 70 mph to just 30 mph.
The developments Thursday came as wrenching wakes got underway for victims James Lovell and Donna Smith and a third victim, James Ferrari, was buried after a funeral mass.
Funeral plans for the fourth victim, Kisook Ahn, were still being finalized.
Meanwhile, another crash survivor, Kelon McFarlane, was expected to announce his intention to sue the MTA, bringing the total who have taken legal action thus far to three.
With Dareh Gregorian