The Family Connection in Exceptional Longevity
THE DRAMATIC INCREASE IN LIFE EXPECTANCY during the past
century is unprecedented in human history. But despite these spec-
tacular advances, we still have limited knowledge of what factors lead
to survival in old age.
Anyone seeking to understand the
determinants of longevity should look
first at family history. Family studies that
go back a century or more provide clear
evidence that longevity does run in families (see Box). These findings closely
agree with a number of studies that have
analyzed further the familial component
of longevity through the pedigree of centenarians. In a study published in Lancet
in 1998, Thomas Perls, director of the
New England Centenarian Study, and
other researchers compared siblings of
102 centenarians with the general population and found that the relative risk of
survival for siblings of centenarians increases with age—to such an extent that
they were approximately four times as
likely to live to 91 as the siblings of people who died at age 73.
In a second study, published in 2002,
Perls and his colleagues compared the
survival of siblings of 444 centenarians
from the New England Centenarian
Bradley Willcox and col-
leagues at the Pacific Health
Research Institute added
to this body of research in
a 2006 article published in
the Journal of Gerontology that
compared the survival of siblings of
348 centenarians with that of the 1890
Okinawan general population cohort. A
survival advantage for siblings of centenarians, for both men and women,
was again reported with approximately
half the mortality of their birth cohort-matched counterparts.
Family Matters
Why are siblings so alike? Is the resem-
blance between siblings’ longevity driven
by genetics or by the environment? Re-
searchers Kaare Christensen, Thomas
Johnson, and James Vaupel (in a study
published in 2006) and A.M. Herskind
and colleagues (in a study published a
decade earlier) found through classic
twin studies that genetic factors account
for about a quarter of the variation in
adult human survival while 75 percent
could be the result of environmental
factors. Because they share 50 percent
of their genes, the correlation in ages at
death among siblings could be attributed
in part to their genetic heritage. It also
could be the result of a common environ-
ment during childhood or, perhaps to a
lesser extent, in adulthood.
