Suddenly feel old? Here's why. We typically think of ageing as a linear process, a slow, steady decline from youth to old age. But recent research is showing that this model of ageing is wrong – we tick along more or less at the same rate until we reach a tipping point, a sudden period of abrupt ageing. These tipping points come roughly when you’d expect, at the onset of early middle age, late middle age, and old age, with around 20-year plateaus in between. So what can we do to stay on our plat