Borrowed Time : The Science of How and Why We Age by Sue ArmstrongAs featured on BBC Radio 4's Start the Week'A rich, timely study for the era of "global ageing"' NatureThe ageing of the world population is one of the most important issues facing humanity in the 21st century up there with climate change in its potential global impact. Sometime before 2020, the number of people over 65 worldwide will, for the first time, be greater than the number of 04 year olds, and it will keep on rising. The strains this is