Sun and colleagues1 report on their analysis of data from the Nurses' Health Study, in which they evaluate the effects of a physically active lifestyle on a composite end point that is intended to model successful ageing. The authors define successful ageing as the absence of nine common age-associated medical conditions, cognitive impairment, disability and mental health limitations in women who reached their mid-70s. Prior studies have consistently shown a benefit of exercise in reducing the risk of the individual conditions that make up their successful-ageing construct. Strong evidence exists for an inverse relationship between level of physical activity and the development of hypertension, …