Scientists Study What Determines People's Longevity

Zhou Zheng

PureInsight | September 24, 2006

[] Longevity and
health are the topics that everyone cares about. From the preservation
of one's health in ancient times to today's modern science, there are
all sorts of opinions on how to improve and maintain one's health.
Modern medicine has started to investigate cells and genes at the
molecular level. But how much influence does a gene have on a person's
longevity? An article published on the New York Times on August 31, 2006 discusses this question. And the answer is quite disappointing.


The article described the health of 92-year-old Josephine Tesauro who
lives in a suburb of Pittsburg, Pennsylvania. She is still very healthy
with a straight back and strong teeth. She can even drive to visit
friends, go to church and go shopping. In contrast, her twin sister has
a dramatically different health situation. She is incontinent, has had
a hip replacement, and she has a degenerative disorder that destroyed
most of her vision. She also has dementia.

The article stated that experts in the aging research felt shocked
after they learned about the two sisters. These twin sisters have
identical genes and grew up in the same family and lived in the same
area, why are their aging and health situations terribly different?

A few decades ago, people thought that one's longevity was determined
by the environment, diet, physical activity and medical care. Later on,
genetic theories became popular. It is thought that due to the
differences in genes, some people are fated to live to be over 100
years old even though they eat red meat freely and smoke cigarettes
heavily. This kind of opinion is still quite popular now.

But recent research discovered that, in general, genes are not that
important in determining people's life span and health condition. In
other words, it is impossible to predict a person's life span according
to how long his or her close relatives have lived.

James Vaupel, the Executive Director of the Max Planck Institute for
Demographic Research, explained that a person's height is closely
related to his genetic heritage. But one's life span is dramatically
different from that. It is difficult to estimate how long a person can
live based on how long his parents lived. Even identical twins have
different life spans. The difference is over 10 years on average.

Human longevity is a fascinating thing. Especially when one gets old,
one might pass away at any moment, and sometimes it is difficult to
tell what the exact reason is. Among different people, some are
physically weaker while others are physically stronger. Of course, the
common thinking is that the stronger ones will live longer. But it is
not always like that. Some people look quite weak but can live for a
long time while others seem to be physically strong and die suddenly.

According to the New York Times
article, some diseases such as Alzheimers or early heart diseases are
more closely related to genetic heritages than cancer and other
diseases. However, even for those diseases, if someone has a high risk
due to the link of genetic heritage, it doesn't mean that person will
definitely have the disease. In fact, the majority of people who are
genetically disposed to certain diseases don't end up with those
diseases. To back up even one step further, even if someone has a
disease, even one with a high mortality rate, it doesn't mean the
person will die from the disease.


Another example given in the article is James Lyons who lives in the
state of Michigan. His father died of a heart attack at the age of 55.
From the onset of the heart attack to his death only lasted 6 hours.
Not only that, his two cousins died at 57 and 50 years, respectively.
The cousin who had died at age 50 was very healthy and energetic. But
one day he just passed away. Because of the family history, when James
reached 50 years old, he started to worry about himself.

However, 25 years has passed. James Lyons is 75 and still very healthy.
He has outlived most members of his family. Why is that? No one knows.

In order to investigate this issue, Dr. Kaare Christensen, a professor
of epidemiology at the University of Southern Denmark, studied twins.
Twins have identical genes and are easier to compare. He and his
colleagues collected the data on all the identical twins (about 20,000
people) born from 1870 to 1910 in three countries - Denmark, Finland
and Switzerland. The results of their investigation indicate that genes
have much less impact on longevity than what the public and scientists
would have predicted. Even twins with identical genes have very
different longevity.

In another research project, scientists analyzed cancer rates in 44,788
pairs of Nordic twins. The results demonstrate that among the many
kinds of carcinomas, only three (breast, prostate and colorectal) have
a noticeable genetic component. And it was not much. If one identical
twin got one of those cancers, the chance that the other twin would get
it was generally less than 15 percent, about five times the risk for
the average person but not a very big risk over all. If it is true that
the cause of a disease is totally So, in the genes, the probability of
the other twin having the same disease should be close to 100% when one
twin develops a disease. Dr. Robert Hoover of the National Cancer
Institute wrote in an accompanying editorial: "There is a low absolute
probability that a cancer will develop in a person whose identical twin
- a person with an identical genome and many similar exposures - has
the same type of cancer. This should also be instructive to some
scientists and others interested in individual risk assessment who
believe that with enough information, it will be possible to predict
accurately who will contract a disease and who will not."

So, in conclusion, what determines how long a person lives? Scientists
still don't know the answer. It can only be explained as an occurrence
with unknown causes.


Regarding one's life span and health, ancient people believed that
those who committed bad deeds would shorten their life spans and die
early. People who did good things would accumulate virtue (De)
and extend their longevity as well as benefit their children and
grandchildren. There were many such examples recorded in the ancient
historical book. According to historical records, Zhu Geliang, the most
famous military strategist in Chinese history, had his life span cut
short because he had hurt too many people in battles.

Looking from another angle, regardless of whether how long a person
lives is random or "fated," if there are indeed heavenly principles,
whether a person does good or bad deeds will still have impact on his
future years.


(1) Live Long? Die Young? Answer Isn't Just in Genes:,


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