Pan Y, et al. - In this Mendelian randomization study, researchers explored the causal relationships of Lp(a) concentrations on ischemic stroke, ischemic stroke subtypes, and Alzheimer disease. They employed 9 single-nucleotide polymorphisms linked to Lp(a) concentrations as instrumental variables. They obtained summary-level data on ischemic stroke and its subtypes from the Multiancestry Genome-Wide Association Study of Stroke consortium with ≤ 446,696 people in Europe. Findings suggested a causal association of high Lp(a) concentrations with an increased risk of large artery stroke but a reduced risk of small vessel stroke and Alzheimer disease. More investigation is required of the mechanism underlying the double-edged sword effect of Lp(a) concentrations on the neurological system.