RESPONSE LETTER TO ROZZINI ET AL.

Abstract

To the Editor: We appreciate your interest in our article and welcome your valuable comments. With regard to the results you report, we also did not find an association between total alcohol consumption measured in grams and the risk of Alzheimer's disease (AD); we found an association between light to moderate wine consumption and a lower risk of AD.1 There are several potential explanations for this finding. One is that of residual or uncontrolled confounding, that is, that there are characteristics of the subjects who consumed mild to moderate amounts of wine that decrease the risk of AD. The study by Geroldi et al.2 found that higher alcohol intake was related to better markers of well-being, and this could result in confounding of the association between alcohol intake and a lower risk of AD. We agree, as you postulate, that this is a possible explanation for our results; it is possible that wine consumption is a marker for characteristics we did not control for that decrease the risk of AD. Our study was observational, and a pitfall of this type of study is the possibility of uncontrolled confounding.3 Uncontrolled confounding by personal characteristics not taken into account or not properly adjusted for may explain recent examples of clinical trials that have not replicated findings of protective associations in observational studies, such as the case of hormone replacement therapy.4 There are plausible biological mechanisms that relate mild to moderate consumption of wine to a lower risk of AD, including improved vascular biology and antioxidant effects.5, 6 Our results are in agreement with other studies7-9 showing an association between wine consumption and decreased AD risk, and other studies have shown an association between moderate intake of any alcoholic beverage and a decreased risk of AD.10-12 Nevertheless, we agree that the only way to exclude confounding as an explanation for reported associations between moderate alcohol or wine intake and a decreased risk of AD is by conducting clinical trials, and we believe that moderate alcohol or wine intake cannot be recommended for the prevention of cognitive decline and AD with the available evidence. Support for this work was provided by grants from the National Institute of Aging AG07232, AG07702, from the Charles S. Robertson Memorial Gift for research on AD, from the Blanchette Hooker Rockefeller Foundation, and from the New York City Council Speaker's fund for Public Health Research.