S T A N F O R D M E D I C I N E

Spring 2000

 

For Alumni
Stanford
MD

 

On the Cover

Bridging Disciplines to Squelch Cholera. 

Cover illustration by Calef Brown.

Stanford Medicine, published quarterly by Stanford University Medical Center, aims to keep readers informed about the education, research, clinical care and other goings on at the Medical Center.

 

sleepy people

live dangerously

By MITCH LESLIE

 

lack of sleep rivals alcohol
in slowing reactions

 

YOU'D GET VERY CONCERNED IF, WHILE WAITING TO BOARD AN AIRPLANE, YOU SAW THE PILOT STUMBLE OUT OF THE AIRPORT BAR. RECENT STANFORD RESEARCH SUGGESTS THAT YOU SHOULD BE JUST AS WORRIED IF YOU SEE THE PILOT YAWNING AND RUBBING HIS EYES.

In a test of reaction times, people who were tired because of disrupted sleep performed about as poorly as subjects who were legally drunk, the researchers report. The study is the first to show severe impairment in people who have only mild to moderate sleep disturbances.

Nelson B. Powell, DDS, MD, leader of the research team, says he hopes that the results will spark talk about the need for safety guidelines to cover sleepiness -- rules that might resemble those already in place for blood alcohol levels.

Alcohol's slowing effect on reaction times is well documented, says Powell, who co-directs the Stanford Sleep Disorders Clinic and Research Center. That is one reason why society demands that people responsible for the safety of others -- truck drivers, train engineers, airline pilots -- limit their alcohol consumption before working.

Yet, Powell notes, society does not seem to be as concerned about the harmful impact of sleeplessness. Powell wants to see that change, so he and five colleagues set out to measure how the sleep disorder sleep apnea affects reaction times.

People with sleep apnea -- about 24 percent of middle-aged men and 9 percent of middle-aged women -- stop breathing multiple times during the night. These interruptions come during sleep, so the patient may not be aware of them, but they prevent the body from settling into a deep sleep and result in daytime drowsiness.

Those with extreme apnea, who are often so tired that they may struggle to remain awake during a conversation or while driving to the corner store, clearly represent a danger. However, Powell's group wanted to learn if less severe forms of the disorder might also compromise safety.

So they recruited 113 patients with mild to moderate sleep apnea and compared their reaction times with those of 80 normal volunteers who had slept well the three previous nights. Members of the healthy group took the reaction-time test sober to provide baseline data. Sober, their reaction times averaged 241 milliseconds. Then they gradually got drunk on orange juice and vodka and performed the test three additional times: once at a blood alcohol level of 0.057 percent (above the legal limit for driving a commercial vehicle of 0.04 percent), again at 0.08 percent (the limit to drive a car in California and many states) and finally at 0.083 percent.

To assess the reaction times, the subjects took 10-minute tests calling for them to push a button whenever a red light flashed. The period between flash and push is the reaction time.

Comparing the two groups on seven measures of reaction time -- including average time, maximum time and average of the 10 fastest times -- showed a surprising degree of impairment in the apnea patients. On all measures, their results were worse than those of the group with a blood alcohol level of 0.057 percent. And on three measures, the apnea patients scored as badly or worse than those who were legally drunk. "That really stunned us," Powell says.

Taking one example, the average reaction time for the drinkers with a blood alcohol level of 0.057 percent was 263 milliseconds (just over a quarter of a second), which increased to 276 milliseconds by the time their alcohol level rose to 0.08 percent. The average time for the apnea patients was 266 milliseconds.

Powell hopes this study, which appeared in the October 1999 issue of Laryngoscope, will start a national discussion about whether rules to protect the public from accidents due to sleepiness are necessary. For example, he suggests that it might be prudent to require airline pilots to pass a reaction-time test before taking off.

"Being arrested for sleepiness -- that isn't going to happen, but maybe it should," Powell says. "It might make people in sensitive positions take responsibility."