A deadly Metro-North train derailment last year in which the “dazed” engineer was found to have sleep apnea has pushed the commuter railroad to look into establishing screening for the condition, which could include measuring operators’ necks and asking them and their spouses about snoring habits.

Metro-North spokesman Aaron Donovan confirmed that the railroad that serves New York City’s northern suburbs is working with unions on sleep apnea screening, but he cautioned nothing has been decided. Any program, he said, “would be for all employees in any safety-sensitive positions.”

While no cause has been established for the Dec. 1 derailment in the Bronx that left four dead and dozens hurt, apnea has gotten much of the attention. Even before the accident, federal railroad officials had been discussing requirements related to sleep disorders. But there is still no national screening requirement for apnea, and railroads around the country have varying practices.

Any screening program that emerges is likely to start with questioning about the subject’s sleep habits and some physical measurements. Overnight sleep-observation studies, which can be time-consuming and expensive, could follow.

Apnea robs its victims of rest because their tongue and throat muscles relax too much during sleep, and they are repeatedly awakened as their airway closes and their breathing stops.

“The person basically gasps himself awake,” said Dr. Gregory Belenky, director of the sleep and performance research center at Washington State University. “It’s very much the functional equivalent of waterboarding.”

Loud snoring is a symptom and apnea is more common in those who are overweight. Having a large neck size, over 17 inches for men, is a risk factor.

In the case of engineer William Rockefeller, who was at the controls during the Metro-North derailment, the National Transportation Safety Board said he was classified as obese at 5-foot-11 and over 260 pounds.

Rockefeller told NTSB investigators that he felt strangely “dazed” before his train hit the curve, which has a 30 mph speed limit, at 82 mph. Asked if he was clearheaded enough to realize he was entering a curve, he replied, “Apparently not.”

Rockefeller’s medical exam after the accident uncovered “severe obstructive sleep apnea,” and when experts studied his sleep, he woke up about 65 times an hour without being conscious of it. As few as five interruptions an hour can make someone chronically sleepy.

The Federal Railroad Administration, with the help of Harvard’s medical school, has set up a website with resources including an apnea questionnaire and a video of a man snoring thunderously and repeatedly waking up to breathe during a sleep test.

James Stem, a lobbyist with the International Association of Sheet Metal, Air, Rail and Transportation Workers, said the website is useful but nationwide rules are needed.

“Fatigue is the No. 1 safety issue in the industry today,” he said.

At Boston’s Massachusetts Bay Transportation Authority, anyone hired to drive a bus or a train is screened for sleep disorders using the Epworth Scale, a questionnaire that asks people to rate their chances of dozing off in various daytime situations, including watching TV and driving but stopped in traffic.

“People with sleep apnea, they fall asleep at stoplights, they fall asleep at meetings during the day,” Belenky said. “They’ll deny any sleepiness and nod off right in front of you.”

If the questionnaire leads to a diagnosis, Boston’s drivers are required to get treatment and comply with it.

A common treatment of obstructive sleep apnea is CPAP, or continuous positive airway pressure, which uses a mask and hose to push a steady flow of air pressure into a person’s airway during sleep. The mask can be programmed to reveal whether a person is following doctor’s orders.

At the Chicago-area Metra network, spokeswoman Meg Riley said there’s no specific test of engineers for sleep apnea, but if their regular exams lead to a diagnosis, the railroad requires treatment and a doctor’s statement that the employee is cleared for work.

The Schneider trucking company, based in Green Bay, Wisconsin, imposed a screening program after finding that fatigue was the top cause of crashes, said spokesman Don Osterberg. Drivers were asked questions about sleepiness and had their neck circumference and body mass index measured.

If a trucker shows potential risk, a sleep study is ordered, Osterberg said. And if apnea is diagnosed, treatment and compliance are mandatory.

Although Schneider pays for the testing and the CPAP masks, health care costs have dropped because accidents were fewer and less severe, Osterberg said — and drivers felt better.

Rockefeller responded well to CPAP and felt more energetic, the NTSB said. His Epworth scale score dropped from 12 (“See the advice of a sleep specialist without delay.”) to 1 (“Congratulations, you are getting enough sleep.”).

(AP)