Division of Epidemiology, Department of Family and Preventive Medicine, University of California, San Diego, La Jolla, CA 92093
In the October 15, 2002, issue of the Journal, Leroi et al. (1) presented an interesting paper suggesting that alcohol consumption is associated with less cognitive decline. However, their analysis was limited by the fact that the possible confounding effect of smoking on the association between alcohol and cognitive function was not reported.
In a prospective analysis, we examined the association of cigarette smoking and alcohol consumption at baseline with risk of poor cognitive function 1318 years later (2). Smoking was associated with increased mortality in men and poorer cognitive function in women. After taking into account the effect of smoking, we found that in women, increasing consumption of alcohol predicted a decline in performance on two cognitive function tests and that consumption of two alcoholic drinks per day predicted decreased performance on the Buschke long-term recall task (2). However, the observed associations were weak, and no clear pattern was observed. Alcohol consumption was not associated with cognitive function in men.
Because cigarette smoking increases the risk of death and/or institutionalization, it may have contributed to the survival bias in the Leroi et al. (1) study. Because cognitive decline has so few known modifiable risk factors, it would be very useful to see the associations after adjustment and stratification for cigarette smoking.
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