With age, the liver decreases in overall size and blood flow is reduced. The liver becomes less efficient at metabolising many substances, meaning that drugs may not be inactivated as quickly in older people. Metabolism of LDL cholesterol decreases, leading to an increase of cholesterol in the blood. The aging liver also becomes less resistant to damage from toxins, and this damage takes longer to repair than in younger people.
Changes in antipyrine clearance (a measure of liver function) and CYPs (liver enzymes) with age (source).
Production of bile decreases with age, increasing the risk of gallstone formation.
Age-related changes in cholesterol, insulin secretion, fat distribution, and inflammation may increase the risk of non-alcoholic fatty liver disease and liver cirrhosis.