APOEε2, the least common of the 3 APOE alleles, has a protective effect for AD and risk and protective effects for several other neurological diseases including stroke, cerebral amyloid angiopathy, posttraumatic stress disorder, age-related macular degeneration, progressive supranuclear palsy, and argyrophilic grain disease.8 Because APOEε2 is less common, we had less power to detect an association. This evidence concerns the gene APOE and progressive supranuclear palsy.