Direct to consumer tests that claim to tell us our biological – as opposed to chronological – age are getting a lot of attention, but what can they really tell us about our health? Science editor Ian Sample talks to Dr Brian H Chen, an epidemiologist at the California Pacific Medical Center Research Institute, who has conducted research into a variety of these tests called epigenetic clocks. He explains what exactly they are measuring and whether, once we have the results, there are any evidence-based strategies we can adopt to lower our biological age