In the first study of its kind, she asked 33 mothers of one-year-olds how much sleep they had got since their babies were born. More than half were getting fewer than seven hours a night. Dr Carroll also took samples of the women’s blood and analysed it for tiny changes to their DNA. These changes are linked to ageing, as well as age-related illnesses, such as heart disease, and higher odds of an early death. The results revealed that the first six months after a baby’s birth are crucial. Lack of sleep in that period sped up ageing – and the risk of ill health. Poor sleep in the next few months did not seem to have an effect.