In an effort to develop a simpler test to identify commercial truck drivers who suffer from severe sleep apnea and who might fall asleep at the wheel, medical investigators have developed a two-stage strategy combining questions about the symptoms of sleep apnea, with body weight data, plus a test for oxygen concentration in the blood when needed. From this combination, they produced a predictive rate of 91 percent for the disorder.

To develop their new test, researchers studied 406 commercial drivers in order to uncover cases of sleep apnea before a crash. Utilizing a level of five or more sleep apnea episodes per hour to define any apnea, 114 drivers were shown to be affected by mild to moderate apnea; in addition, 19 drivers had 30 or more episodes per hour to demonstrate severe sleep apnea. (Sleep apnea is a serious sleep disorder in which an affected person pauses in breathing during sleep for 10 seconds or longer and then resumes breathing after a very brief arousal.)

According to the authors, sleepiness accounts for between 31 to 41 percent of the major crashes of commercial vehicles. In 2001, large trucks were involved in 429,000 crashes. Nearly 5,000 were fatal. The researchers said that the simplest strategy they employed depended first on responses to questions about three apnea-related symptoms.

Then they looked at body mass index (BMI) data because obesity is a major obstructive sleep apnea factor. In addition, they examined a risk score that combined information about symptoms with BMI as well as about age and sex.

When they added oximetry to measure oxygen level in the blood, the test was 91 percent sensitive. If oximetry was not employed, it was 81 percent predictive. They called their new tool the multivariable apnea prediction index. The study appears in the second issue for August 2004 of the American Thoracic Society's peer-rerviewed American Journal of Respiratory and Critical Care Medicine.