Wolozin et al1 report a lower prevalence of probable Alzheimer disease (AD) in patients using pravastatin or lovastatin in a cross-sectional study involving 56 790 patient files from 3 large centers. The authors state that the study does not show any causal relationship between use of pravastatin or lovastatin and lower prevalence of AD and that the association may be due to confounding variables, such as lack of specific focus on AD by physicians generating the databases. In this respect, it is important to note that, clinically, dementia of Alzheimer type and vascular dementia can hardly be differentiated. Furthermore, there is increasing evidence that atherosclerosis interacts with risk factors for AD2 and that patients who have had a stroke have an increased risk to develop Alzheimer dementia.3 The authors stress the need for a rigorous prospective clinical trial. Such a trial is the Prospective Study of Pravastatin in Elderly at Risk (PROSPER),4 which is currently under way in Scotland, Ireland, and the Netherlands. The PROSPER is a double-blind, randomized, placebo-controlled trial investigating the effect of 40 mg/d of pravastatin in an elderly population; 5804 persons aged between 70 and 82 years with cardiovascular disease or at increased risk have been randomized. Major end points are fatal and nonfatal stroke, myocardial infarction, and total mortality. Furthermore, annual neuropsychological tests are performed to investigate the effect of pravastatin treatment on cognitive decline. Mean follow-up will be 3½ years. The results of the study are expected in 2002.