An automated method of determining a measure of a subject's heart age comprising the steps of: prompting a user for a plurality of inputs, each relating to an attribute of the subject, each attribute defining one or more of a demographic status of the subject, a lifestyle status of the subject, a physical condition of the subject and a medical history of the subject; receiving, from the user, a plurality of said inputs; determining from said received inputs, a set of parameters for which input data has been received as input from the user; selecting a heart age calculation algorithm from a predetermined set of heart age calculation algorithms according to said set of parameters; and calculating a heart age for the subject according to the selected algorithm; and providing as output said calculated heart age.