According to a recent study, people ages 100 and older are the fastest-growing segment of the U.S. population, with female centenarians outnumbering the males 5-1. Their secret?

Dr. Thomas Perls, associate professor of medicine at Boston University Medical Center and director of the New England Centenarian Study, told the Washington Times, "Genetics plays an exceptional role in longevity ... so looking at the family tree is important." Findings from the Centenarian Study suggest that longevity does run in families -- the sibling of a centenarian is four times more likely to live past 90 than the general population.

Good genes, however, are just part of the story.

Related Resources: Tracing Your Medical Family Tree | Determining Your Ancestry Through DNA