“How a society treats its elderly people is a yardstick of its civilisation,” said the world's oldest man, who celebrated his 112th birthday last month. Inevitably, Tomji Tanabe (one of Japan's 30 000 centenarians) was asked about the secret of his longevity. “Avoiding alcohol and maintaining a daily regime to keep me young” was his reply. Dying was not on his agenda, he said; he wanted to live indefinitely.

If most of us experienced old age in such a positive way we could perhaps simply sit back and marvel at our species' increasing longevity. Sadly, this is not the case, and governments in nearly all countries are waking up to the fact that their ageing populations pose formidable economic, social, and health challenges.

The latest UN Report on World Ageing (executive summary www.un.org/esa/population/publications/WPA2007/wpp2007.htm) shows the scale and pace of what some term the demographic tsunami. World population is increasing at 1.1% a year, but the number of people over 60 is increasing at 2.6%. The number of people over 60 tripled between 1950 and 2000, …