Researchers tested drowsiness and attention in 16 healthy young men
exposed to either sleep deprivation or alcohol consumption, or to
both at once.
They found that the combination of moderate alcohol consumption -
within legal limits for driving - and restricting sleep to just five
hours a night produced greater drowsiness and more deficits in
attention than either sleep restriction or alcohol intake alone.
The combined effects of alcohol and sleep deprivation lasted two to
three hours, the study found.
“No amount of alcohol intake has been deemed safe when under the
influence of sleepiness through either poor or inadequate sleep, or
being awake when the body (should be) asleep at night,” said study
co-author Clare Anderson of the Institute of Cognitive and Clinical
Neuroscience at Monash University in Australia.
“Our take-home message would therefore be to avoid alcohol when
feeling sleepy and to have a short nap before attempting to drive or
undertaking any other safety critical task,” Anderson said by email.
Previous research has shown that alcohol can impair motor
coordination, critical thinking skills and decision-making and may
lead people to take more risks than they might while sober. Sleep
deprivation, meanwhile, has been linked to distraction and delayed
In the current experiment, men between 18 and 27 years old were
assessed four times. Researchers asked the participants to rate
their level of drowsiness, tested their focus and attention with
eye-movement measurements, and examined their response speed to
stimuli by seeing how fast they could push a button when an image
flashed on a computer screen.
At the start of the study, researchers ran men through these tests
without any intervention. Then they repeated the same assessments
after alcohol or sleep deprivation alone or in combination.
Outside the experimental conditions, the men typically went to bed
between 10:00 p.m. and 1:00 a.m. and woke up between 6:00 a.m. and
9:00 a.m. To create a state of sleep deprivation, men were allowed
to rest only from 2:00 a.m. to 7:00 a.m. the night before the test
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During alcohol assessments, performed more than four hours after men
woke up for the day, participants were given enough to drink to
raise their blood alcohol level to 0.05 percent - the legal driving
limit in Australia, the UK and many European countries. The legal
limit in the U.S. is 0.08 percent.
Researchers tested the men’s attention and vigilance one hour after
they drank alcohol and again every 30 minutes for two hours.
When men were deprived of sleep and also given alcohol, they were
most impaired about 90 minutes after they drank, the study team
reports in Human Psychopharmacology.
It took about 2.5 hours for men to return to their performance
levels before having the drink, even when they got rest breaks
between rounds of testing.
Beyond its small size, other limitations of the study include the
focus on healthy young men, which means the results might be
different for older people or individuals with physical or mental
health issues that can impact driving ability.
Even so, the findings suggest that people who no longer feel
“buzzed” from drinking may still be unsafe behind the wheel, said
Russell Griffin, a researcher at the University of Alabama at
Birmingham who wasn’t involved in the study.
“So while you may feel fine driving home when you leave that party,
that feeling can make a turn for the worse on the drive home,
particularly since alcohol increases the feeling and effects of
sleep deprivation,” Griffin said by email.
The results should also serve as a reminder to drink in moderation.
“The body is only able to metabolize, or remove, a little bit of
alcohol at a time, so the more alcohol a person drinks, the more
alcohol is circulating through their system and the higher the
impairment,” Griffin said.
SOURCE: http://bit.ly/2wgQYaz Human Psychopharmacology: Clinical and
Experimental, online July 18, 2017.
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