WHITE PLAINS, N.Y. — The engineer on a New York commuter train that derailed at high speed last year, killing four people, had a serious sleep disorder that interrupted his rest dozens of times each night, federal investigators disclosed Monday.
The National Transportation Safety Board’s medical examination of engineer William Rockefeller uncovered ‘‘severe obstructive sleep apnea,’’ according to documents released by the agency. Rockefeller told investigators he felt dazed and hypnotized just before the crash.
The documents did not say whether the disorder contributed to the Dec. 1 crash on the Metro-North railroad. The NTSB said its analysis of the information and any determination of the cause would come in a later report.
Rockefeller’s lawyer and union leader have suggested the engineer nodded off on the morning of Dec. 1 as his train raced toward a sharp curve in the Bronx, where it derailed. The curve had a 30 mile-per-hour speed limit; the train was going 82.
Attorney Jeffrey Chartier said a few days after the accident that Rockefeller experienced a nod or ‘‘a daze,’’ almost like road fatigue or the phenomenon sometimes called highway hypnosis. Anthony Bottalico, leader of the rail employees union, said Rockefeller ‘‘basically nodded.’’
The NTSB report said a sleep study was ordered because Rockefeller ‘‘did not exactly recall events leading up to the accident.’’
The test found that while Rockefeller slept, he had about 65 ‘‘sleep arousals’’ per hour. Scientists say as few as five interruptions an hour can make someone chronically sleepy. The report said Rockefeller’s apnea apparently was undiagnosed before the accident.
The NTSB noted that sleep apnea is not mentioned in Metro-North’s medical guidelines.
Metro-North spokesman Aaron Donovan said the railroad was reviewing the documents.