Alcohol consumption can have direct and indirect effects on cognitive function (e.g., impaired driving, increased risk of cerebral hemorrhage). In magnetic resonance imaging (MRI) studies, moderate alcohol consumption has been associated with greater brain atrophy but less white-matter disease. Mukamal and colleagues address the risk of confirmed dementia in a large cohort of adults with repeated measures of alcohol use.

The authors used data from the Cardiovascular Health Study to perform a nested case-control study of alcohol consumption and the risk of incident dementia. Of the 3,660 participants who completed MRI examinations, 3,608 also completed a 100-point Modified Mini-Mental State Examination. Researchers used a four-stage screening process, including a full neuropsychiatric battery, to determine dementia, with subsequent diagnostic confirmation by panels of experts. Candidates were interviewed yearly about the quantity of alcohol they drank. The authors used the case-control approach to assess the relative odds of incident dementia according to alcohol consumption.

Median follow-up was 6.1 years in patients with dementia and 6.0 years in control subjects. Subjects who consumed one to six drinks per week had 54 percent lower odds of developing dementia than subjects who abstained from alcohol. Subjects who consumed 14 or more drinks per week had the highest odds ratio (OR). The inverse association tended to be linear in women and U-shaped in men. Women who consumed seven or more drinks per week had a lower OR than women who consumed six or fewer drinks per week. The OR decreased in men who drank one to six drinks per week, then rose with consumption of seven or more drinks per week. Subjects who were positive for the APOE e4 allele showed an inverse association with dementia, with the exception of heavier drinkers; the odds of dementia were more than threefold higher in APOE e4–positive subjects who drank 14 or more drinks per week than among abstainers.

The authors conclude that light alcohol consumption (i.e., one to six drinks per week) has a protective effect against dementia. However, given the other effects that alcohol may have, the authors caution against making specific recommendations.