Provided herein are methods of detecting or determining aging and/or oxidative damage in tissue, including placental tissue, skin, kidney and brain tissue. One embodiment provides a method for detecting or determining aging in body tissue, comprising measuring one or more markers of aldehyde oxidase 1 (AOX1) expression or activity in a biological sample, wherein the level of AOX1 expression or activity, or of the one or more markers, is indicative of aging in the tissue. Also provided herein are methods of treating a disease or condition associated with ageing or oxidative damage in one or more cells or tissues, comprising administering to a subject in need thereof an inhibitor of AOX1.