Researchers and medical professionals already know that chronic, excessive alcohol consumption causes cognitive and motor deficits. Operating as a central nervous system depressant, alcohol produces a dose-dependent decrease in cognitive and motor functioning. A new study by Edith Sullivan and colleagues, published in the May issue of Alcoholism: Clinical & Experimental Research, takes neuropsychological research to a new level: specifying which functions are most affected by alcohol, suggesting which neural systems are implicated, and searching for any age-alcohol interaction.
"This study gives us in-depth coverage of the neuropsychological decline that is associated with alcoholism," said Marlene Oscar-Berman, professor of neurology and psychiatry at Boston University School of Medicine, and research scientist at the Boston Veteran Affairs Healthcare System. "This study speaks to behavioral abnormalities that are inferred from what’s happening to the brain. It’s about the brain, as expressed in behavior."
"We know that cognitive capacities and motor system functions are impaired in alcoholics," explained Sullivan, associate professor of psychiatry at Stanford University School of Medicine and the study’s lead author. "But cognition is a ‘catch word’ that includes a lot of different capacities, like problem solving, remembering things, recalling verbal and non-verbal materials, and spatial orientation. Similarly, the motor system comprises many different capacities, including activities like upper and lower limb functions, the ability to walk or run, and balance." Sullivan wanted to examine these functions more closely in recently detoxified male alcoholics.
"We chose men who had been inpatients in a VA facility," she explained, "so we knew they hadn’t had a drink for about a month, they were receiving good nutrition, and they were in relatively good physical condition." Even so, said Sullivan, the men continued to show mild yet significant cognitive and motor deficits. The greatest deficits were in gait and balance, followed by visuospatial abilities, and cognitive processes called ‘executive functions.’
Sullivan explained that her findings of deficits in gait (the general ability to walk) and balance were alarming because it had previously been thought that this ability recovers with abstinence from alcohol. "Yet when we challenged them with elements of a typical road-side sobriety test," she said, "we found that they were really quite unstable. They had a hard time walking a line with their eyes open, as well as closed. They also had a hard time standing on one foot, or standing still in one position." She added, "this is not a benign finding. These people may be at increased risk for an age-alcohol interaction. As we get older, we all become unstable in our gait and balance; someone who already has a history of alcoholism may be at particular risk for falling."
The other areas of deficit involved visuospatial capacity which, for example, refers to someone’s ability to read a map, and ‘executive functions’ - including problem solving, the ability to place things in order (both temporal ordering and sequencing of events), and working memory. The presence of these deficits implicates at least two principal neural systems: the cerebellar-frontal system and the corticocortical system connecting the prefrontal and parietal cortices. Knowing which parts of the brain are involved in alcohol-triggered disruption is important because of implications for identifying risk as well as opportunities for recovery.
Oscar-Berman noted the connection between this study’s findings and what she called the "premature aging hypothesis." She explained that about 50 years ago, researchers discovered (using autopsies) that the brains of alcoholics resembled the brains of people with no alcohol history but who were much, much older. "Their brains were smaller, reduced in size," she said. Subsequent research has found that younger alcoholics typically don’t show this ‘premature-aging effect,’ but older alcoholics do. "That is," she said, "if you have been an alcoholic, when you get to be about 50 years old or so, all of the things that are supposed to happen to you when you get older instead can happen earlier and faster." Indeed, Sullivan’s study found a synergism between alcohol and aging, particularly regarding motor function such as gait and balance.
"The recovering alcoholic has a ways to go," said Sullivan. "Just because a person has been through a 30-day patient stay and has shown some recovery doesn’t mean the recovery is complete. In fact, some of these functions may be gone forever. If that’s the case, the alcoholic needs to be aware of this and figure out a way to deal with it in his job, in his day-to-day activities, [and in his life]."