It is already well-known that the brains of long-term alcoholics atrophy and shrink, the study authors say, but the new findings are the first evidence that cigarette smoking might contribute to that atrophy, particularly in grey matter of the parietal and temporal lobes.
Fifty to 90 percent of alcoholics also are smokers, according to Dieter Meyerhoff, PhD, a radiology researcher at SFVAMC and the principal investigator of the study
"Just looking at the amount of tissue mass lost due to either drinking or smoking, alcoholics who smoke show a greater loss in some regions of the brain compared to alcoholics who don't smoke," says Meyerhoff, who also is a professor of radiology at the University of California, San Francisco.
The study, which was published in the August 2005 issue of Alcoholism: Clinical and Experimental Research, compared 37 recovering alcoholics between the ages of 26 and 66 with a control group of 30 healthy light drinkers. The researchers used magnetic resonance imaging, a safe, non-invasive imaging technique, to measure brain volumes of the study participants.
They discovered that the more severe the tobacco habit, the greater the brain injury. "In smoking alcohol-dependent individuals, smaller regional [brain] volumes are related to greater cigarette-smoking severity," according to the study findings, with severity measured by level of nicotine dependence, cigarettes smoked per day, and years of smoking.
The alcoholics (24 smokers and 13 non-smokers) averaged around 400 drinks per month for three years prior to the study; the light drinkers (seven smokers and 23 non-smokers) averaged between four and 11 drinks per month before the study and had no history of alcohol abuse or dependence. The alcoholics were sober for approximately one week before the study began.
The study uncovered no apparent differences in brain volume between smoking and non-smoking light drinkers.
Another key finding was that among non-smoking alcoholics, there was a direct relationship between brain volume and cognitive function: the higher the volume, the better the function. However, no such relationship was apparent among smoking alcoholics, according to co-author Timothy Durazzo, PhD, an associate radiology researcher at SFVAMC. Nor has such a relationship been measured before in previous studies on alcohol abuse and brain volume, he says.
"And this makes us wonder if what has been reported in the literature of alcoholism could have been obscured or distorted by combining smokers and non-smokers in the same studies," Durazzo adds.
In their paper, the researchers speculate that smoking "disrupts these [brain] structure-function relationships," possibly through its detrimental effects on brain volume or on brain neurochemistry.
Meyerhoff and his co-authors emphasize that their results are retrospective -- that is, they discovered the apparent effects of smoking during statistical analysis of the participants in an earlier study they conducted on alcoholism and its effects on the brain. They then went back, re-classified each study participant as smoking or non-smoking, and analyzed brain volumes accordingly.
The authors say that if replicated in other studies, their results will raise several potentially important questions. The first is whether recovering alcoholics should also be treated for smoking -- and if so, at what point during their treatment. At present, alcohol treatment programs such as Alcoholics Anonymous do not discourage smoking or even address the issue, they say.
Beyond that, says Durazzo, there is the potential effect of smoking on cognitive dysfunction, which is common among older long-term alcoholics. "Right now, our study participants are relatively young, around 50," he notes. "But will the combination of smoking and drinking, or continued smoking during abstinence from alcohol, put them at greater risk for cognitive dysfunction as they age?" Finally, says Meyerhoff, there is the question of whether smoking has an effect on physical recovery from alcohol abuse. "In alcoholics who stop drinking, we know that there is recovery from at least some of these injuries to the brain -- but is this recovery affected by continued smoking?" Meyerhoff and his team are conducting a study to explore that question right now.
In the future, the researchers plan a prospective study that will use MRI to compare brain volumes between smoking and non-smoking light drinkers and smoking and non-smoking alcoholics, with the hope of replicating the results of their current retrospective study.
Other authors of the study include Stefan Gazdzinki, PhD, of UCSF and the Northern California Institute for Research and Education (NCIRE); Colin Studholme, PhD, of UCSF; Enmin Song, PhD, of NCIRE; and Peter Banys, MD, of SFVAMC and UCSF.
The research was supported by a grant from the U.S. Public Health Service that was administered by NCIRE.
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