Studies of Brain Size in Alcoholic Men and Women

by National Institute of Health

(Page 2 of 2)

Only one study has compared the volumes of specific brain structures of alcoholic and nonalcoholic men and women. This study measured the volume of the hippocampus, a structure critical for memory function, and found that alcoholic women had smaller right and left hippocampi than nonalcoholic women; alcoholic men only had smaller right hippocampi in comparison with nonalcoholic men. The alcoholic women reported fewer years of heavy drinking, a later age of onset, and lower estimated lifetime alcohol consumption compared with the alcoholic men. DeBellis and colleagues also reported smaller hippocampal volumes in a small group of adolescent alcoholics compared with their nonalcoholic peers. The authors did not report the results by gender.

Two studies examined the size of the corpus callosum, a large fiber bundle connecting the two cerebral hemispheres, which is essential for communication between the hemispheres. Reduction in the size of the corpus callosum may be a marker for damage to long white-matter tracts connecting the two hemispheres, and thus an indicator of the overall health of the brain's white matter. One study showed that after controlling for brain size, alcoholic women had significantly smaller corpus callosum areas than both nonalcoholic women and alcoholic men. However, other research has failed to find significant differences between alcoholic and nonalcoholic women in corpus callosum area.

The methods used to measure corpus callosum size were similar in these studies, and the severity of alcoholism in the two samples did not differ. The reason for the inconsistent results is not clear. Subsequent studies, however, using more sensitive measures to evaluate white-matter microstructure (diffusion tensor imaging [DTI], described in the article in this issue by Rosenbloom and colleagues) have reported evidence for brain damage among alcoholic women when compared with female control subjects matched for brain size. It is possible that the white-matter damage in female alcoholics may be better detected using DTI than conventional MRI techniques.

Only two studies have compared total cerebral volume among alcoholic and nonalcoholic men and women. Both studies used high-resolution, full-volumetric MRI scanning techniques and found strong evidence for greater brain shrinkage among alcoholic women compared with alcoholic men, even though the alcoholic women started heavy drinking later in life and had consumed less alcohol in their lifetimes. (However, in both studies, alcoholic women drank as much as or more than alcoholic men in the 6 months immediately preceding the scan, suggesting that brain volume may be more influenced by recent alcohol consumption than by earlier alcohol use.)

In another approach, Pfefferbaum and colleagues used an MRI method that sampled a block of tissue made up of a set of axial slices (tissue sliced along the horizontal plane) comprising approximately 25 percent of total brain volume. This study found less brain shrinkage among alcoholic women than men.

The inconsistency between the results obtained by Pfefferbaum and colleagues and the results from the previously described studies does not appear to be accounted for by differences in lifetime alcohol consumption between the samples of alcoholic women, although few of the women in the Pfefferbaum study had a history of hospitalization for alcoholism, and all of the women in the other two studies had been hospitalized at some point. It is possible that differences in imaging methods contributed to the different results, because Pfefferbaum's study measured only a portion of the cerebrum, and the other studies measured the volume of the entire cerebrum.

In addition to the studies of brain structure reviewed above, one study using magnetic resonance spectroscopy (MRS) to compare male and female alcoholics found that, in frontal lobe gray matter but not frontal lobe white matter, alcoholic women had a significantly greater deficit in concentrations of N-acetylaspartate (a marker for neuronal integrity) than alcoholic men. These MRS findings are consistent with the report by Hommer and colleagues that gray-matter damage distinguishes alcoholic women and men to a greater extent than white-matter damage.

Conclusion

Compared with alcoholic men, alcoholic women have received little research attention. This is particularly unfortunate because there is good evidence that many of the behavioral aspects of alcoholism progress more rapidly among women than among men. It is important to determine what role, if any, alcoholism-related brain damage plays in the progression of alcoholism. Although most of the recent studies suggest that women are more vulnerable to alcohol-induced brain damage than men, it would be premature to state this conclusively. Nearly all the recent studies of gender differences in this area have been conducted by only two research groups, one of which has consistently found evidence for greater brain damage among alcoholic women, whereas the other group has not. The field of gender studies in alcoholism needs more investigators to join in this work in order to resolve the conflicting results that currently characterize this field.

About the Author

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