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Who Are Centenarians? (continued
pg. 4)
Siblings of Centenarians Live Longer (See Reference 15, Below)
While conducting a population-based study of centenarians, we
were struck by the large number of subjects who also had long-lived
siblings. Comparing the survival rates of siblings of centenarians
and of the siblings of a similar birth cohort who died in their
early seventies, we found the siblings of our centenarian subjects
had a 4 times greater chance of surviving to their early nineties.
Using town censuses, we located and recruited 102 centenarians
(10 males, 92 females) and their families living in the Eastern
Massachusetts area. The control group was a similar birth
cohort consisting of people born in 1896, but who died at
73 years of age in 1969 (n=77, 28 males, 49 females). We located
the next-of-kin of these subjects using data provided by the
Massachusetts State Registry of Vital Records and subsequently
death notices appearing in the 1969 Boston Globe. Birth
dates and current age or age at death of siblings of both
groups were obtained from next-of-kin. By comparing subjects
with similar years of birth, we controlled for time-dependent
influences on survival such as trends in health care, illness
outbreaks (e.g. the influenza epidemic of 1919), war (e.g.
WWI), and fluctuations in the economy (e.g. the boom of the
1920's and the Great Depression). The centenarians had a total
of 456 siblings (233 males, 223 females) and the 73-year-olds
had a total of 240 siblings (121 males, 119 females). The
two groups of siblings were not statistically different in
birth place, birth year, years of education, marital status
and religion.
Standard techniques of survival analysis showed that the two
groups of siblings differed significantly in survival to older
ages (see figure). Survival rates were the same (relative risk=1)
at younger ages, but were progressively higher for siblings
of centenarians after age 70. By age 90-94, the relative risk
for survival was 3.9 (95% CI: 3.2, 4.9) for the female siblings
of centenarians and 5.1 (95% CI:4.1, 6.4) for the male siblings.
Relative risks beyond age 90-94 continued to increase, but were
not statistically significant because of small numbers of subjects
at these extreme ages. For any age after 65, siblings of centenarians
had a 42.4% lower hazard of death (95% CI: 0.334,0.538, p<0.0005).
Female siblings of centenarians survived to a median age of
80 (95%CI: 79,85) and the males survived to a median age of
76 (95% CI: 73,79), while female siblings of the 73-year-olds
survived to a median age of 74 (95% CI: 69,77) and the males
survived to a median age of 73.5 (95% CI: 71,75).
Interestingly, we observed the centenarian probands had more
siblings (4.5 siblings/ proband) compared to the seventy-three
year old probands (3.2 siblings/proband). Several factors could
have contributed to this finding. Children whose parents were
still alive may have been able to recall the family pedigree
better than the children of the septuagenarians who died in
1969. However we note that few centenarians assisted their children
in reporting data. There could also be some other hidden ascertainment
bias, although this seems less likely given the similarity in
demographic characteristics between the two groups of probands.
In fact, it may well be true that centenarians come from larger
sibships. We (T.T.P.) recently reported the finding that 19%
of female centenarians had children after the age of forty compared
to 6% of women who died at the age of 73 years (1). Perhaps
relatively larger sibships occur in these families because there
is also an associated ability to have children later in life
and therefore to have more of them.
Centenarians continued
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