Drunk drivers may not know they’re impaired

PROVIDENCE – A new study led by Peter J. Snyder, vice president of research at Lifespan, shows that alcohol intoxication impairs reasoning and problem-solving abilities in such a way that a person who is drunk may believe he or she has recovered enough to drive safely.
The study, published in the August issue of the American Psychological Association’s journal Experimental and Clinical Psychopharmacology, is the first to explore how cognitive abilities are affected by rising and declining alcohol concentrations, and how people’s perception of recovery differs from actual recovery.
Alcohol-related car accidents kill about 17,000 Americans each year, and the risk of a crash increases with higher blood alcohol levels. What the study focused on is the other half of the curve: how people’s skills recover as their alcohol level declines and they sober up.
The researchers assessed 20 college students at multiple time points over two days, documenting their subjective perception of intoxication and testing their cognitive skills, including visuomotor speed, learning efficiency, executive function and short-term memory, by having them navigate through a maze that was easy if they followed simple rules.
The study found that as blood alcohol declined, some skills improved, but others – most notably executive function, a “higher-order” skill – remained impaired. The partial recovery, however, made the students feel they were getting sober.
“While our study supports past research, the real new piece of information that we have from this study is that unlike basic functions that are commonly studied in alcohol research such as motor speed and information processing speed, executive functions don’t recover as quickly.” said Snyder, who is also professor of neurology at The Warren Alpert Medical School of Brown University.
“The subjective feeling that you are drunk does recover more quickly,” he said. “This explains why so many individuals feel subjectively that they are able to get into a car and be able to drive and feel safe. But that subjective impression does not mesh with the actual recovery in terms of higher-order executive functions.”
Those higher-order functions are important for driving skills and for making critical judgments such as when to cross through an intersection or change lanes, Snyder said.
Making people aware of this disconnect might be helpful in education and prevention efforts, Snyder said, underscoring “the real risk with respect to the decision to drive when alcohol impaired.”
The study was funded by a grant to Snyder from the University of Connecticut, where he worked before joining Lifespan last year. The research team also included Jennifer Cromer, of the University of Connecticut; Jason Cromer, of Picower Institute for Learning and Memory and the Massachusetts Institute of Technology; and Paul Maruff, of CogState Ltd. and the Centre for Neuroscience at the University of Melbourne in Australia.