Subject groups did not differ in age. Men weighed more, were taller, and had larger intracranial volumes than women, but alcoholics and comparison subjects did not differ significantly on any of these measures (
+Table 1). However, there were two characteristics on which the alcoholics and nonalcoholics differed. Alcoholics had completed fewer years of education (
+Table 1), and more of the alcoholics smoked cigarettes: 51 (65%) of the alcoholics were smokers, compared with only four (10%) of the nonalcoholics (χ
2=18.0, df=1, p<0.0001). Male and female alcoholics did not differ in the proportion of smokers in each group. Sixty-three (80%) of the alcoholics and 35 (90%) of the nonalcoholics were right-handed (χ
2=1.6, df=1, n.s.).
On admission there were no significant differences in nutritional status between male and female alcoholics as measured by total serum protein (for men, mean=7.30 G/dl, SD=0.64, and for women, mean=7.31 G/dl, SD=0.54) (t=0.69, df=77, n.s.), albumin (for men, mean=4.33 G/dl, SD=0.46, and for women, mean=4.20 G/dl, SD=0.42) (t=–1.81, df=72, n.s.), and transferrin (for men, mean=267.8 mg/dl, SD=41.4, and for women, mean=289.2 mg/dl, SD=54.6) (t=1.73, df=77, n.s.). The mean time between hospital admission and MRI scan was 22.2 days (SD=7.8) for male alcoholics and 21.5 days (SD=6.1) for female alcoholics (t=0.48, df=77, n.s.). The alcoholic women reported significantly fewer years of heavy drinking (mean=8.5 years, SD=5.7) than the alcoholic men (mean=14.3 years, SD=7.5) (t=3.76, df=75, p<0.001), but they did not differ significantly in their estimates of total lifetime alcohol consumption (for men, mean=703 kg of ethanol, SD=602, and for women, mean=480 kg of ethanol, SD=516) (t=1.73, df=75, n.s.) or in their estimates of consumption during the 6 months preceding admission (for men, mean=24.1 kg of ethanol, SD=15.0, and for women, mean=24.2 kg of ethanol, SD=14.1) (t=–0.05, df=75, n.s.). Thirty-one (72%) of the alcoholic men and 28 (78%) of the alcoholic women had at least one first-degree relative with a history of alcoholism or problem drinking (χ2=0.36, df=1, n.s.). Thirty-three (77%) of the alcoholic men and 32 (89%) of the alcoholic women met criteria for an axis I disorder other than substance abuse disorders (χ2=0.91, df=1, n.s.). These were primarily mood or anxiety disorders.
Although the alcoholic men had a greater mean volume of sulcal CSF and smaller mean volumes of gray and white matter than nonalcoholic men, only the differences in gray and white matter volumes achieved statistical significance (
+Table 2). Ventricular volumes were virtually identical in the two groups. In contrast, all of the mean brain and CSF volumes of the alcoholic women were significantly different from those of the nonalcoholic women (
+Table 3). The largest difference in brain volume between alcoholic and nonalcoholic women was in gray matter, which was 11% smaller among the alcoholic women (
+Table 3). Adjusting for years of education by using ANCOVA did not change any of these results. Alcoholics who were cigarette smokers did not demonstrate any significant differences in brain volumes from alcoholic nonsmokers. Similarly, alcoholics with and without a family history of alcoholism or a personal history of axis I psychiatric disorders other than substance abuse disorders did not differ significantly in any brain volumes. Brain volumes did not differ between right-handed and left-handed individuals.
When we adjusted brain volumes for intracranial volume, it was possible to include all four groups in a single analysis. The results are shown in
+Table 4. All of the brain ratios, except for ventricular volume/(intracranial volume–ventricular volume), differed significantly between alcoholics and comparison subjects (ANOVA, main effect for diagnosis). The alcoholics had a larger proportion of their intracranial volume occupied by CSF than the comparison subjects and had a smaller proportion of intracranial gray and white matter than comparison subjects.
There was a significant interaction between diagnosis and gender in the analysis of gray matter ratio. Simple contrast tests within genders between alcoholics and nonalcoholics indicated that the difference between the groups was due to alcoholic women having a smaller proportion of gray matter than nonalcoholic women (
+Table 4). In contrast, alcoholic men had only a slightly smaller ratio of gray matter to remainder of intracranial volume than nonalcoholic men (
+Table 4).
There were no significant interactions between gender and diagnosis for CSF or white matter ratios. However, there was a significant interaction between diagnosis and gender in the analysis of ventricular ratios. Simple contrast tests indicated that this interaction was due to the alcoholic women having larger ventricular ratios than the nonalcoholic women (
+Table 4).
The only difference in the ratios between women and men, irrespective of diagnosis, was in the proportion of intracranial volume contents occupied by white matter (
+Table 4). Women had proportionally less white matter than men. Adjusting for years of education by ANCOVA did not change any of the results. Comparisons between alcoholics who were cigarette smokers and alcoholics who were not smokers revealed no significant differences in brain volume ratios; comparisons between alcoholics with or without a family history of alcoholism also revealed no significant differences. Alcoholics with or without other axis I disorders did not differ in brain volume ratios.
Among the alcoholic patients, none of the measures of alcohol consumption (years of heavy drinking, lifetime alcohol consumption, and recent alcohol consumption) or number of first-degree relative reported to be alcoholic correlated significantly with any of the direct measures of brain volume or any of the brain volume ratios. Similarly, years of education did not significantly correlate with any direct or ratio measure of brain volume among either the alcoholics or nonalcoholic comparison subjects. In contrast, age did correlate significantly with many brain volume measures, particularly among the comparison subjects. The ratio measures were more highly correlated with age than were the brain volumes unadjusted for intracranial volume. Among the unadjusted volumes, only CSF among the healthy comparison subjects was significantly correlated with age (r=0.55, N=39, p<0.001).
Correlations between age and the ratios of gray matter (r=–0.64, N=39, p<0.001), white matter (r=–0.49, N=39, p<0.001), and CSF (r=0.66, N=39, p<0.001) were all significant among the healthy comparison subjects. Ventricular volume was not related to age among alcoholics or comparison subjects. Among the alcoholics, only gray matter ratio significantly correlated with age (r=–0.29, N=79, p<0.01).
+Figure 1 and
+Figure 2 show scatter plots of the relationships between age and the ratio of gray matter to the remainder of the intracranial volume among men and women, respectively. The slopes of the regression lines are very similar across the four groups, suggesting that, at least over the age range we examined, alcohol may not accelerate normal aging of the brain. However, given the limitations of analysis of cross-sectional data, this interpretation must be viewed with caution. It also appears that by early in their fourth decade of life, alcoholics, particularly alcoholic women, have considerably smaller brain volumes than nonalcoholics.