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Senior Citizen Health & Medicine
Type A Personality Not Linked to Heart Disease as
Long Assumed, Says New Study
High, low blood
pressure more strongly influenced by genes as people age
August 29, 2006 A new and very large study has
found absolutely no connection between the hard-driving personality
(often called Type A) and heart disease, contrary to previous studies
and conventional wisdom. Although human genes contribute significantly
to a person's health and behavior, these two kinds of traits aren't closely linked at all. Some traits, especially
high or low blood pressure, were found to be more strongly influenced by
genes as a person aged, says the study appearing this month in the
Public Library of Science.
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Health & Medicine |
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These findings are among the first of a massive,
10-year effort to measure the genes and traits of a single population of
closely related people. Conducted jointly by Italian and Sardinian
researchers, the U.S. National Institute on Aging, and bio-statisticians
at the University of Michigan, the project recruited 6,148 people aged
14 to 102 in four clustered villages on the island of Sardinia in the
Mediterranean Sea. The sample represents 62 percent of the population of
the Lanusei Valley surrounding the four villages.
Sardinia was chosen as an ideal laboratory for
genetic studies because of its isolation and relative stability, said
Gonηalo Abecasis, associate professor of biostatistics in the U-M School
of Public Health. He and U-M post-doctoral fellow Wei-Min Chen led
statistical analysis on the project. "If you did this study in New York
or Detroit, you'd find people with all sorts of genetic backgrounds,"
Abecasis said.
The Sardinian study group is essentially one giant
family: 95 percent of the people in the study had all four of their
grandparents born in Sardinia and one family encompassed 600 cousins.
"If you look at small families it's much harder to
separate what's genes and what's environment," Abecasis said.
Each of the study participants took a personality
test and received a half-day health assessment that included tests for
cholesterol levels and other blood factors, an electrocardiogram, an
arteriogram and blood pressure measurement. Environmental factors such
as smoking and diet were also measured, though they have yet to be
analyzed.
This is only the first pass on what promises to be
a very rich source of new genetic insights, said co-author David
Schlessinger of the National Institutes on Aging in Baltimore. "We're
expecting an avalanche of data in the next few months."
Although the statistical analysis showed that there
is a clear genetic component for each of the 98 traits examined and that
some genetic factors influence many traits at once, no connection was
established linking personality and cardiovascular function.
"We didn't see it," Schlessinger said. "Maybe it's
there, but we didn't see it."
Height was found to be 80 percent genetic,
cholesterol about 40 percent, and behavior traits 10 to 20 percent,
Abecasis said.
Earlier studies had assigned higher percentages for
the genetics of behavior, but Abecasis thinks that happened because of
statistical biases created by the twin studies that have traditionally
provided this kind of data.
"To avoid such problems, this analysis of more than
34,000 relative pairs focused on more distantly related individuals,"
Abecasis.
For most traits, genes have relatively more
influence when a person is younger, but some traits, especially high or
low blood pressure, were found to be more strongly influenced by genes
as a person aged.
Schlessinger says this is because some traits would
have cumulative effects that only show themselves with a longer
lifespan. For example, genes that result in a poor ability to scour
deposits from arteries could eventually lead to elevated blood pressure,
but only after the deposits had accumulated over time.
Having established some of the genetic
correlations, the next step is to find the specific molecular
differences that account for variation, Abecasis said.
"The most exciting part comes next. And we now have
a better idea of who to study for what condition." In order to
accomplish this next step, 10,000 genetic markers have been
characterized for each participant and 500,000 genetic markers have been
characterized in a subset of participants.
Study participants will also be tracked for several
more years to see if the genetic data has been successful at predicting
disease, said Schlessinger, who first began thinking about the ambitious
Sardinian study 10 years ago. "There is nothing else quite like this."
Though the Sardinian population is uniquely
homogeneous, Abecasis and Schlessinger expect that their results will be
comparable across populations and consistent with other studies.
Abecasis and Chen co-wrote the paper "Heritability
Of Cardiovascular and Personality Traits in 6,148 Sardinians," with
Schlessinger of the National Institute on Aging, a division of the
National Institutes of Health which leads the federal research effort on
aging and the medical, social and behavioral issues of older people.
>> For more on Abecasis, visit:
http://www.sph.umich.edu/csg/abecasis/index.html
>> For more on Chen visit:
http://www.sph.umich.edu/csg/chen/index.html
>> National Institute on Aging -
http://www.nia.nih.gov/
>> Public Library of Science -
http://www.plos.org/
>> UM Center for Statistical Genetics -
http://csg.sph.umich.edu/
>> Gonηalo Abecasis lab-
http://www.sph.umich.edu/csg/abecasis/
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