NORWALK - Published reports say the engineer in the deadly Metro-North train derailment may suffer from the common sleep disorder sleep apnea.

Doctors say that what is so dangerous about sleep apnea is that people who have it may think they have gotten enough hours of sleep, not realizing that the disorder disrupts sleep thousands of times in a night.

Union officials say Metro-North engineer William Rockefeller admits he was nodding off at the controls and by the time he woke up, it was too late to slow the train down before it came off the tracks. Four people were killed and dozens were hurt.

Doctors say that shift workers are generally tired people, especially if they change shifts, and that they sometimes have to resort to taking medications that will keep them awake and alert during the working hours.