Women who sit for 10 hours or more a day have faster-ageing cells than those who exercise every day, new research has found. In a sample of 1,500 women, aged 64 to 95, researchers from institutions including the University of California and San Diego State University looked at telomeres – chromosome-protecting caps at the end of DNA strands. Telomeres naturally shorten with age and are also shortened by lifestyle factors such as stress, smoking and obesity. The study, which was published in the American Journal of Epidemiology, measured information over one week, during which time women wore an accelerometer, a device that measures movement. They found that, among those women who did less than 40 minutes of physical activity a day, those who sat longest had shorter telomeres, making them biologically eight years older than their more active counterparts. However, sitting time did not seem linked to telomere length for women who did at least 30 minutes of physical activity a day – the national recommended guideline. Although the study has limitations, sitting for long periods has already been linked to obesity, some forms of cancer, and type II diabetes, so getting up and moving more can only be a good thing.