Scientists in recent years have developed ways to measure biological age by tracking chemical changes in DNA that occur naturally as people age but occur at different times in different people. These so-called ‘epigenetic clocks’ have proved to be better predictors of lifespan and health than chronological age. In a new study, Yale researchers used one such clock, appropriately named “GrimAge,” to ask two questions: How much does chronic stress accelerate that biological clock? And are there ways to slow it down and extend a healthy lifespan?