With 70,000 US centenarians today and some 800,000 predicted by 2050, it is no surprise that one of the most comprehensive research programmes into what makes a centenarian is being carried out in the US. The New England centenarian study is following the fortunes of centenarians living in eastern Massachusetts and has already made a series of intriguing discoveries.1,4,5 First, nearly all the centenarians were in good health and able to live relatively independently until they were at least 90. Second, there was evidence that longevity does run in families. Overall, siblings of centenarians in the study were four times more likely to survive into their early 90s than those who didn't have centenarians in the family. In two families, three and four siblings lived to 100 and more.

Another finding was that women who had a child in their 40s had an increased likelihood of living to 100, indicating that their reproductive system (and quite likely the rest of their body) was ageing more slowly than usual.

Similar research is being conducted in Florida - the traditional home of the US blue-rinse brigade. About 100 centenarians have been located, 69 per cent of them women. Three-quarters had parents who lived well past 80 and into their 90s, usually with little or no history of cancer or strokes. Few of the Florida centenarians had experienced serious illness in the past 20 years of their life, most had never smoked. A surprisingly high proportion - some 40 per cent - had had a college education and, with few exceptions, they had experienced

long marriages. A third had been married or lived with the same person for 50 years or more and only 6 per cent had never been married.

One of the most reassuring findings to come from international research on very old people is that many live out their days with their mental faculties largely intact. In the Swedish centenarian study carried out in Lund, only a quarter of subjects had dementia and over half were able to get on with the normal activities of daily living with little or no help.6 In France, Denmark and the US, more cognitive impairment has been recorded in centenarians. But everywhere they are studied, extremely old people seem to be naturally calm, easy-going and optimistic.

There must be something particularly special about being Japanese. At 77 for men and 83 for women, Japanese life expectancy is the highest in the world, and one part of the country - the island of Okinawa - has the highest proportion of centenarians on the globe.

This success in battling the Grim Reaper is widely attributed to dietary restraint - not just the fish oils, vegetables and soya products beloved of the Japanese, but the daily calorie intake, which is 20 per cent lower in Okinawa than in the rest of Japan.