Biological ageing – the rate at which our bodies decline over time – varies between people and drives the world’s most fatal diseases, including heart disease, dementia and cancers. Genes linked to ageing that could help explain why some people age at different rates to others have now been identified by scientists in Edinburgh and Cologne. An international study using genetic data from more than a million people suggests that maintaining healthy levels of iron in the blood could hold a key to ageing better and living longer.