From the New Scientist: "It is becoming clear that people who break through the 90-plus barrier represent a physical elite, markedly different from the elderly who typically die younger than them. Far from gaining a longer burden of disability, their extra years are often healthy ones. They have a remarkable ability to live through, delay or entirely escape a host of diseases that kill off most of their peers. Supercentenarians - people aged 110 or over - are even better examples of ageing gracefully. ... As a demographic group, they basically didn't exist in the 1970s or 80s. They have some sort of genetic booster rocket and they seem to be functioning better for longer periods of time than centenarians. ... The average supercentenarian had freely gone about their daily life until the age of 105 or so, some five to 10 years longer even than centenarians, who are themselves the physical equivalent of people eight to 10 years their junior. ... Alzheimer's disease, the most common form of dementia, is relatively rare among centenarians yet, intriguingly, autopsies reveal that the brains of the oldest old, who had shown no outward sign of dementia, are sometimes riddled with the lesions associated with Alzheimer's disease. The basis of this resilience to Alzheimer's is largely unknown. The simple fact is that many people who become centenarians seem able to tolerate damage that would significantly harm less robust individuals, and although many suffer from dementia as death draws near, most remain mentally agile well into their nineties."