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."
|