WASHINGTON - The medical review board of the Federal Motor Carrier Safety Administration is expected to issue recommendations this month that would require commercial vehicle drivers with obstructive sleep apnea to get treatment before they are allowed to drive.

The recommendations are designed to curb drowsiness among commercial vehicle drivers, especially truckers, as well as act on medical findings regarding the sleep disorder.

People who have obstructive sleep apnea wake up frequently during sleep because the disorder causes their airways to partially close. The constant awakening, once every minute or two in severe cases, makes them unusually drowsy during their waking periods. That makes them especially risky for driving over-the-road vehicles.

A major contributor to the condition is obesity, says Allan Pack, director of the Center for Sleep and Respiratory Neurobiology at the University of Pennsylvania and adviser to the medical review board.

The board is expected to recommend that commercial truckers be required to undergo a sleep study once they reach a certain level of obesity. But there apparently is no agreement yet at what level of obesity should the benchmark be set.

If the agency eventually approves the recommendation, drivers would have to be treated for the condition to get certified. The range of treatment modules available for obstructive sleep apnea includes surgery or putting on a mask while sleeping to allow air into the body's airway.

A study by the agency of commercial driver license holders showed that 17.6 percent of licensed truckers had mild sleep apnea, another 5.8 percent had moderate sleep apnea and 4.7 percent suffer from severe sleep apnea.

According to one expert, drivers with obstructive sleep apnea are 2 1/2 times more at risk of being involved in a crash. And the crashes tend to be more severe.

The Owner-Operator Independent Drivers Association, according to a spokesman, is not in favor of mandatory tests for obstructive sleep apnea on the basis of being overweight, except if a direct causal relationship between the ailment and obesity could be established.