A biological clock in people's DNA could tell could tell scientists how long they will live.
Researchers have found that chemical changes in DNA can help us understand people's "biological age" - a measure of how old their body is that seems to be able to predict when people are going to die.
Scientists found that people whose biological age showed them as older than their real age were more likely to die sooner. That still held true, even accounting for other factors like smoking and heart disease.
Four independent studies tracked 5,000 people for up to 14 years. Researchers measured each of their biological ages, and then compared it over time.
Scientists found that the link between biological age and the chance of death held up.