Scientists have located an area on chromosome 4 linked to exceptional longevity, a new report says. The study, published in todays edition of the Proceedings of the National Academy of Sciences, tracked 308 subjects older than 90 in an attempt to find a genetic component to longevity. "Most investigators would say that longevity is just too complicated a trait to be influenced by only a few genes," co-author Louis Kunkel of the Howard Hughes Medical Center says. "But we took a chance that this was the case because in lower organisms such as nematodes, fruit flies and yeast, there are only a few genes that need to be altered to give a longer life span."

An earlier finding that centenarians often have long-lived siblings set the researchers to work. They studied groups of siblings, called sibships, in which one member was at least 98 and had at least one brother older than 91 or sister older than 95. A genome-wide comparative DNA analysis using 400 markers found a region on chromosome 4 that had a higher than expected amount of allele-sharing among the geriatrics. The researchers caution that this study is only a starting point in the long process of finding the gene or genes directly responsible for longevity because the implicated area of chromosome 4 may hold as many as 500 genes.

Centenarians, having lived nearly 20 years longer than the average Jane or Joe, often maintain markedly good health. They age slowly, the researchers suggest, and either significantly delay or avoid entirely age-associated diseases such as cardiovascular disease, stroke, diabetes, cancer and Alzheimer's disease. "Were not trying to find the fountain of youth," co-author Thomas Perls says. "If anything, were trying to find the fountain of aging well."