The National Transportation Safety Board said Wednesday that if the Metro-North Railroad had properly screened employees for sleep disorders, a train driver’s undiagnosed sleep apnea might have been detected before it led to a derailment in the Bronx last December that killed four and injured at least 61 passengers.

The lack of screening for sleep disorders was among the issues highlighted in a final report released by the safety board Wednesday following its investigations into the Bronx train wreck and four other major Metro-North accidents between May 2013 and March 2014.

In the December derailment in the Bronx, the engineer told investigators he became dazed before the train he was driving barreled into a tight curve without slowing down.

Metro-North, a commuter railroad serving New York City suburbs in Connecticut and Westchester County, is run by the Metropolitan Transportation Authority.

The safety board’s report said the MTA’s New York City Transit, which operates the city’s subway and bus system, was the only one of its divisions that “meaningfully screens, evaluates and addresses treatment” of severe obstructive sleep apnea in relevant employees.