Many people who get sleepy while driving have undiagnosed nighttime breathing disorders, new study findings show.

Researchers found that about 1 out of every 30 drivers regularly felt sleepy while driving on the highway, corresponding to a 13-fold increase in the risk of a car accident.

Compared with more alert drivers, sleepy drivers tended to:

• Be overweight
• Snore
• Have high blood pressure
• Be sleepy in the morning

Researchers found that people who were suspected of having a sleep disorder ran a high risk of having a car accident while waiting to see a sleep specialist, for which the wait time was over a month.

Researchers studied 124 people who were referred to a sleep center for observation due to excessive sleepiness.

During the period while they were waiting for their appointment:

• 5.4% had a car crash
• 16.4% almost had a wreck
• 16.2% fell asleep behind the wheel
• 30.6% fell asleep at work

In addition, some of the people were fired or demoted during the waiting period.

The study authors maintain that "Many of these accidents and other problems could have been avoided if the sleeping problems had been diagnosed and treated sooner".

American Journal of Respiratory and Critical Care Medicine October, 2000;162:1407-1412 and Meeting of the American College of Chest Physicians San Francisco, California, October, 2000