At ages 102 and 104, Bessie and Sadie Delany were probably the most unlikely pair of authors in history. Yet in 1993, they produced a best-selling oral history, Having Our Say: The Delany Sisters' First 100 Years. "Sadie," Bessie once asked, "do you suppose we're ever going to die?" Reflecting on that question after Bessie died in 1995, Sadie wrote, "It did seem rather peculiar both of us living past 100, outliving everybody around us." But new research suggests the Delany sisters' extraordinarily long lives weren't just a fluke of nature.
In fact, brothers and sisters of centenarians are much more apt to survive to age 100 than other people and have lower mortality rates throughout life, according to a study* published in the June 11, 2002 issue of the Proceedings of the National Academy of Sciences . The finding, the latest in a series of studies supported by the National Institute on Aging, (NIA) that have found certain families are predisposed to long lives, could be a major clue in the effort to demystify exceptional longevity.
In the study, Thomas Perls, M.D., director of the New England Centenarian Study in Boston, John Wilmoth, Ph.D., of the University of California, Berkeley, and other researchers analyzed data collected from 444 families that had at least one member living to age 100 or older. According to the analysis, sisters of centenarians had about one-half the risk of dying at any given age compared to the national average. Brothers of centenarians had similarly low mortality rates, except during the teenage years and young adulthood. These decreased mortality rates greatly enhanced the odds that siblings of centenarians would become centenarians themselves. Compared to the general population, brothers of centenarians were 17 times more likely to achieve age 100, and sisters were at least eight times more likely to reach this age.
"This striking finding provides further evidence that centenarians and their relatives are a special group in that they appear to be more resistant to disease or they survive disease better throughout the lifespan. This survival advantage is likely due to genetics and environmental factors, but the roles of each of these factors are still unclear. Studying these individuals could help us understand the factors that contribute to long, healthy lives," said Evan Hadley, M.D., NIA Associate Director for Geriatrics and Clinical Gerontology.
Previously, in an analysis of a smaller cluster of families, Dr. Perls and his colleagues found that siblings of centenarians have a four times greater chance of living into their early 90s than the general population. Other studies have also found familial patterns of exceptional longevity. Although these familial clusterings might be related to environmental or socioeconomic factors, there is evidence that genetic effects are important, too. University of Utah researchers found brothers, sisters and other first-degree relatives of the long-lived tend to live longer lives than cousins and other more distant relatives, suggesting that a small number of genes might influence exceptional longevity. In 2001, Dr. Perls and his colleagues found a region on chromosome 4 that is "highly suggestive" of genetic predisposition to exceptional longevity.
Further studies are being conducted in an attempt to replicate this linkage in other populations. Some studies suggest that exceptionally long-lived people may transmit unusually good protection against major diseases of aging to their children, and that these protective factors are evident in these offspring well before they reach extreme age. Investigators have discovered, for instance, that 60- and 70-year-old children of centenarians may be less prone to cardiovascular disease because they have high levels of HDL ("good") cholesterol and low levels of LDL ("bad") cholesterol. Identifying and characterizing these and other familial patterns are key steps in understanding the role of genetic, environment and socioeconomic factors in long-term, healthy survival.
In addition to longevity studies, the NIA supports numerous health-related genetic and environmental studies worldwide. In Iceland, for instance, 15,000 people are participating in the Age, Gene/Environment Susceptibility Study (AGES), a longitudinal study of cardiovascular and other physical changes that occur over time.
T. Perls, J. Wilmoth, R. Levenson, M. Drinkwater, M. Cohen, H. Bogan, E. Joyce, S. Brewster, L. Kunkel, and A. Puca, "Life-long sustained mortality advantage of siblings of centenarians," Proceedings of the National Academy of Sciences , vol. 99, No. 12, June 11, 2002, pp. 8442-8447.
The NIA, a component of the National Institutes of Health, leads the federal effort in supporting and conducting basic and clinical research on aging and the special needs of older people. For information about the NIA, visit the website at www.nia.nih.gov  .