TWO groups of genes influence longevity. The first are those associated with serious diseases, which centenarians are less likely to have. The second group are longevity enabling genes, which are more likely to be present in centenarians and to influence the rate of ageing.Dr Bradley Willcox is co-principal investigator of the Okinawa Centenarian Study and professor of geriatric medicine at the University of Hawaii. “There are two [longevity gene] superstars: ApoE and FOXO3A,” he says.His team, including twin brother Dr Craig Willcox, has found that a genetic variation (or allele) in the FOXO3A gene is strongly associated with longevity. “About half of centenarians have at least one copy of the protective allele of FOXO3A. If you have two protective alleles of FOXO3A you are 300 per cent more likely to live to be 100.”It is not known precisely how FOXO3A increases longevity. “It mainly acts as a protector against physiological stress. [It] reduces free radical damage, enhances DNA repair, makes the body more energy efficient, helps the body recognise and kill off cancer and other aberrant cells,” says Brad Willcox.A variation in the ApoE gene, which has an impact on cardiovascular disease and dementia, is the only other variant that has also been sufficiently replicated in studies to show that it appears less frequently with advancing age.”There are going to be probably in the order of 100 genes that contribute to longevity. They’ll all have a small effect, and they’ll have different effects in different people,” says Brian Morris, professor of molecular medical sciences at the University of Sydney and Bosch Institute.”But one of the very important findings that has come out of all the research is that someone who has the good genes for long life yet has a bad diet and lifestyle can reduce their chances of living to an old age substantially.”