How old are you, really? Communicating chronic risk through 'effective age' of your body and organs

In communicating chronic risks, there is increasing use of a metaphor that can be termed 'effective-age': the age of a 'healthy' person who has the same risk profile as the individual in question. Popular measures include 'real-age', 'heart-age', 'lung-age' and so on.Here we formally define this concept, and illustrate its use in a variety of areas. We explore conditions under which the years lost or gained that are associated with exposure to risk factors depends neither on current chronological age, nor the period over which the risk is defined. These conditions generally hold for all-cause adult mortality, which enables a simple and vivid translation from hazard-ratios to years lost or gained off chronological age. Finally we consider the attractiveness and impact of this concept.Under reasonable assumptions, the risks associated with specific behaviours can be expressed in terms of years gained or lost off your effective age. The idea of effective age appears a useful and attractive metaphor to vividly communicate risks to individuals.