Heavy drinkers may have noticeable impairments years later, study finds

SAN DIEGO, CA — A person’s tolerance to alcohol may grow stronger when they drink larger amounts more frequently, but that doesn’t mean heavy drinkers are better at performing everyday functions any better after a few drinks.

A recent study finds that long-term heavy drinkers may be able to perform better on certain fine motor tasks after several drinks than people who drink less often, but their cognitive functions are still deeply — and potentially dangerously — impaired.

Researchers from the U.S. Department of Veterans Affairs sought out to examine the effects of heavy drinking on cognitive and fine motor functions over the course of time. While frequent drinkers may develop a stronger tolerance to alcohol than those who drank occasionally, does that mean the heaviest drinkers saw less harmful effects on their ability to function with time?

People drinking beer, alcohol
A person’s tolerance to alcohol may grow stronger when they drink larger amounts more frequently, but that doesn’t mean heavy drinkers are better at performing everyday functions any better after a few drinks. (Photo by Mattias Diesel on Unsplash)

“The theory of behavioral tolerance to alcohol posits that greater experience with drinking to intoxication leads to less impaired cognitive and psychomotor performance,” the researchers write in their background statement. “However, the degree to which behavioral tolerance develops or changes over time in adults due to repeated heavy alcohol drinking has not been clearly demonstrated.”

Researchers examined data over six years on 155 participants in the Chicago Social Drinking Project, a study that looked at the effects of various legal substances, such as alcohol and caffeine, on a person’s behavior.

Analyzing whether or not heavy and light drinkers displayed any tolerance changes or impairment from the start of the study to a follow-up after five years, two testing phases took place. Heavy drinkers were classified as people who consumed 10 to 40 drinks a week over two years, while light drinkers were those who had no more than six drinks in a week.

The first challenge tested fine motor skills and had participants take part in the Grooved Pegboard Test, which involved a rotation of pegs inserted into holes on a board. The second and more complex challenge, known as the Digit Symbol Substitution Test, tapped into the participants’ motor skills as well as short-term memory and cognitive processing. In this phase, individuals were shown a grid of symbols that corresponded with various numbers and then given 90 seconds to recall the symbols on a sheet with just the numbers.

Participants were given a dose of alcohol before each test and then retested at various intervals within three hours.

Both groups showed poorer results after consuming alcohol. And while heavy drinkers displayed less impairment with the simpler pegboard challenge, they weren’t as successful when it came to the symbol test. Light drinkers didn’t display behavioral tolerances on either test phase.

Compared to light drinkers, heavy drinkers reported lower impairments, but time and testing levels changed results.

“The most important thing about the study is that despite heavy drinkers’ extensive experience with alcohol, increased speed of metabolism, and lower self-perceived impairment, we show that on a more demanding task they are just as impaired as light drinkers,” explains lead researcher Dr. Ty Brumbeck in a press release.


To translate the tests to real world examples, Brumbeck explains that the pegboard test would be similar to using a key to open a car door, while the symbol substitution challenge would be akin to driving the car. He points to someone who might have had several drinks at the bar, but doesn’t believe they’re drunk and thus in fine condition to drive home.

“So, if this person tends to perceive herself as less impaired, she gets up from the table and walks to the door, pushes the door open, and walks to her car. These simple motor functions may not provide sufficient feedback for her to decide she is too drunk to drive,” he says. “Furthermore, when she gets to her car and unlocks the door and even puts the car in gear, she may not be perceiving impairment in these simple tasks. However, once she begins to drive, the cognitive and psychomotor demands increase significantly but the decision to drive has already been made based on the earlier simple tasks.”

Brumbeck concludes that people may believe they’re less impaired because they showed an ability to perform a less demanding task with ease — but even the strongest of drinkers aren’t able to build a tolerance that allows them to bypass the most challenging, and in the example above, potentially dangerous situations.

“The take-home message here is that tolerance to alcohol is not equal across all tasks and is not protective’ against accidents or injuries while intoxicated, because it may in fact lead the heavy drinker to judge that they are not impaired and attempt more difficult tasks,” he says. “Making such decisions in the moment is highly risky, because it is based on faulty information.”

This study’s findings were published in the March 2017 edition of the journal Psychopharmacology.


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