STUDY OBJECTIVE: To quantify the risk of cognitive impairment with use of lipid-lowering drugs. DESIGN AND DATA SOURCES: Literature search through MEDLINE and EMBASE databases; data from seven observational studies were analyzed. MEASUREMENTS AND MAIN RESULTS: We quantified the risk of cognitive impairment first with the use of any lipid-lowering drug, and then specifically with the statins, using the random effects model. We tested for heterogeneity using the Q statistic as well as quantitatively using the Ri statistic. All seven studies provided data for statin users, and five provided data only on use of lipid-lowering drugs. Compared with patients not receiving lipid-lowering drugs, the relative risk of cognitive impairment with any lipid-lowering drug was 0.62 but was not statistically significant (95% confidence interval [CI] 0.28-1.38), and the relative risk with statins was 0.43 and was statistically significant (95% CI 0.31-0.62). CONCLUSION: Lipid-lowering drugs--in particular, the statins--seem to lower the odds of developing cognitive impairment. Randomized, controlled trials are needed to address the efficacy of these agents specifically in different types of dementia.