Does Alcohol Prevent Dementia?
Abstract & Commentary
Source: Ruitenberg A, et al. Alcohol consumption and risk of dementia: The Rotterdam Study. Lancet. 2002;359:281-286.
Light-to-moderate alcohol consumption may lower the risk of dementia, according to a recent report from the Rotterdam Study. As part of this prospective, population-based cohort study from the Netherlands, participants were asked to complete a food frequency questionnaire that included self-report of alcohol intake. Patients were subsequently examined over a 6-9 year period to determine the incidence and type of dementia they developed. Ruitenberg and colleagues compared individuals who never drank alcoholic beverages to those who consumed light amounts (> 1 drink per week but < 1 drink per day), moderate amounts (1-3 drinks per day), and heavy amounts (> 3 drinks per day) of spirits. The type of alcoholic beverage was taken into account, as well as a number of possible confounders such as age, gender, diabetes, hypertension, educational attainment, smoking, and body mass index. Great care was taken to exclude individuals from the analysis who were already suffering from dementia or who had other factors that might render their self-report unreliable.
A remarkable 99.7% success rate was achieved in follow-up of 5395 cases. Most participants in the study were older than 55 years of age. As a group, men in the study consumed more alcohol than women. As the amount of alcohol consumption increased, so did the percentage of subjects who smoked and who completed greater amounts of education. Among the more than 5000 participants in the study, a total of 197 developed dementia, representing an incidence rate of 6.1 cases per 1000 persons per year. A total of 146 patients developed Alzheimer’s disease (74%). Of these, less than 10% were thought to have a mixture of Alzheimer’s disease and vascular dementia. An additional 29 patients (15%) were thought to have a purely vascular dementia, and 11% were diagnosed with other forms of dementia.
For the population as a whole, alcohol consumption of 1-3 drinks per day was found to lower the risk of dementia by 42% (95% CI, 10-62%). This effect appeared to be more prominent in men than women, but was evident in both genders. The effect of alcohol appeared to be most significant in lowering the risk of dementia secondary to cerebrovascular disease. The risk of vascular dementia was reduced by 70% among those who drank 1-3 glasses of alcohol per day. There was no evidence that the type of alcohol consumed (wine, beer, hard liquor, or fortified wine) influenced the risk of dementia. Drinking more than 3 glasses of alcoholic beverages per day was not associated with protection against dementia, nor was there an increased risk documented in this study.
Commentary
This is a well-executed epidemiologic study that provides support for the hypothesis that moderate alcohol consumption can reduce the risk of dementia. Consistent with these newly reported findings, at least one previous study from the Bordeaux region in France found that wine consumption could reduce the risk of dementia (Rev Neurol. 1997;153:185-192). One limitation of these studies is their reliance on self reports of alcohol consumption obtained through food intake questionnaires. While this approach can lead to reliable estimates of nutritional intake under many circumstances, self-reports of alcohol consumption are often subject to underestimation. The frequency and extent of alcohol consumption is likely to be correlated with other aspects of lifestyle, which may have an effect on the risk of dementia, falsely imparting the appearance that alcohol is the responsible agent.
Nevertheless, Ruitenberg et al took care to exclude many potential confounders and present some of the strongest evidence to date that alcohol can reduce the risk of dementia. Since the most robust effect was seen on incidence of vascular dementia, they suggest that alcohol’s risk-reducing capacity could be related to effects on vascular risk factors, as is postulated to be the case in terms of alcohol’s effects on risk of stroke and heart disease. It should be noted that binge drinkers and those with alcohol abuse problems were excluded from this analysis. Apart from documenting a lack of protection from consuming more than 3 drinks a day, this study does not address the issue of the harmful effects of excessive alcohol intake on the brain. The harmful neurologic effects of alcohol abuse are well documented, and its dangers need to be reinforced to patients who may misinterpret the results of the Rotterdam Study or use it to justify alcoholism. —Norman R. Relkin.
Relkin, MD, PhD, Associate Professor of Clinical Neurology and Neuroscience, New York Presbyterian Hospital-Cornell Campus, is Assistant Editor of Neurology Alert.
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