The Federal Motor Carrier Safety Administration estimates that about 28 percent of commercial drivers suffer from the disorder. The 2002 study found that 10 percent had either moderate or severe apnea had least mild obstructive sleep apnea, a condition in which individuals obstruct their own airways while sleeping. What can result are interruptions in breathing lasting several seconds at a time, loud snoring and non-restful sleep.

This, in turn, can prove fatal on the road.

Sleep apnea is rarely recognized by its sufferers, so NTSB said it may never be known to what extent the condition is the cause of 5,000 fatal large truck and another 250 fatal bus crashes each year. But last week, a Utah motorcoach driver who was also a school bus driver “blacked out” behind the wheel while transporting a marching band through Idaho. The resulting crash killed a band instructor who tried to correct the wheel and injured several students. While it was unknown if she had sleep apnea, the driver had recently passed a physical and had an excellent driving record. Investigators were reportedly examining her hours of service records.

FMCSA notes on its Web site that drivers with or suspected of sleep apnea should be disqualified until the condition is successfully treated or ruled out entirely.

FMCSA's Medical Advisory Board last year recommended a formal screening program to detect sleep apnea in commercial drivers, but such a program has yet to be implemented. NTSB called on FMCSA to provide guidance to drivers, employers and physicians on identifying and treating sleep apnea. When those treatments are successful, NTSB recommended that only then can drivers receive medical approval on their CDL medical certification.