The present invention provides a medicament for preventing and/or treating cognitive impairment, in particular Alzheimer's dementia, comprising 2-methyl-2-[(4-{(1E)-3-[2-(4-methylbenzoyl)-1H-pyrrol-1-yl]prop-1-en-1-yl}benzyl)oxy]propionic acid or a pharmaceutically acceptable salt or solvate thereof.