Although the mechanisms may differ, vascular dementia and Alzheimer's disease have been linked to lipid levels. Therefore, modifying lipid levels and improving endothelial function could lower the risk of dementia in older persons. Jick and colleagues used the General Practice Research Database to study the relationship between the use of statin drugs and the development of dementia. The database includes information on more than 3 million patients of British general practitioners, and the data can be linked to hospital, pharmacy and demographic records.

The researchers identified 24,480 patients 50 to 89 years of age who had received at least one prescription for a statin medication at any time and 11,421 patients who had hyperlipidemia but were not treated with lipid-lowering drugs. A control group of 25,000 patients in the same age group was also identified from the database. Patients with alcoholism, drug abuse, cancer, multiple sclerosis, psychosis, amyotrophic lateral sclerosis, parkinsonism, Down syndrome, liver or kidney disease, epilepsy and stroke were excluded from the study. The three groups of patients were followed for six years to monitor the development of dementia.

During the follow-up period, 284 patients developed documented dementia. Each of these patients was matched by age and sex with up to four control patients from the same practice. The relative risks of developing dementia related to statin use and untreated hyperlipidemia were calculated. These estimates were adjusted for age, sex, history of coronary or cerebrovascular disease, hypertension, smoking and body mass index. The relative risk of dementia in patients with untreated hyperlipidemia was not significantly reduced when compared with that of patients from the original control group. Conversely, the relative risk in patients receiving statin medications was reduced to 0.29.

The authors conclude that the risk of developing dementia is reduced by 37 to 70 percent in patients 50 years and older who use statin medications. This conclusion is consistent with the effects of these drugs on other vascular conditions, such as myocardial infarction and stroke. Although an observational study cannot prove cause, the beneficial effects of statins on endothelium, as well as the influences on lipid metabolism, could explain mechanisms to prevent dementia. Because of the observed size of the protective effect and implications, the authors call for more studies.