It has long been apparent, although not widely recognized,
that wealth is associated with greater longevity. This becomes obvious when looking at data
obtained on life expectancies at age 65 by Katelin P. Isaacs and Sharmila
Choudhury in The Growing Gap in Life Expectancy by Income: Recent Evidence and Implications for the Social Security Retirement Age.
It is often argued that life expectancies are increasing for
both men and women, so it makes sense to raise the age for social security
retirement as a means of saving money for the system. These data clearly show that rise, but they
also indicate that the poorest, neediest workers, have gained very little in
terms of longevity and would be penalized by an increase in retirement age. This wealth effect is interesting because of
what it means for social security policy, but also because of what it implies for
society. One can reasonably argue that those
with higher incomes have better access to healthcare and have more money to
spend on healthy life styles, but it is difficult to make that correlation
scientifically. Could there be a more
direct link between life expectancy and some other attribute?
Some researchers are beginning to suspect that life
expectancy and intelligence are correlated.
That is one of the many enlightening insights obtained by reading Carl
Zimmer’s book She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity. The understanding of intelligence has been
obscured by faulty early attempts to measure it. Often tests were encumbered by cultural
assumptions which penalized those with alternate backgrounds leading them to be
labeled mentally deficient. Zimmer
points out that decades of improved testing indicate that an individual’s
performance on different types of tests may vary, but there appears to be a
general correlation in the sense that a person who does well on one type of
test will generally do well on a variety of tests. In other words, a person will possess a value
for a quantity referred to as g, general intelligence.
“When scientists give people
tests on different abilities, their scores are correlated. If people are very good at recalling
information from stories, for example, they also tend to do well in recalling
words from lists. Different tests for
logical reasoning correlate with each other as well. In turn, these broad abilities—such as
reasoning, memory, spatial ability, processing speed, and vocabulary—correlate
with each other. Psychologists can
measure this underlying correlation with a single factor known as g, short for
general intelligence.”
One of the most interesting intelligence studies was
performed by Scotland several generations ago.
It was interesting because it used a quality test, and because it was
applied to its entire population of eleven-year-old students. This, much later, produced a treasure trove
of information as the lives of many of these children could be traced and
outcomes such as longevity could be tallied.
“On June 1, 1932, the government
of Scotland testes almost every eleven-year-old in the country—87,498 all
told—with a seventy-one-question exam.
The students decoded ciphers, made analogies, did arithmetic. The Scottish Council for Research in
Education scored the tests and analyzed the results to get an objective picture
of the intelligence of the Scottish children.
Scotland carried out only one more national exam, in 1947. Over the next couple of decades, the council
analyzed the data and published monographs before their work slipped away into
oblivion.”
In 1997, a researcher studying intelligence named Ian Deary
happened upon a reference to this work.
He and colleagues resurrected the tests and the data from them in order
to extract as much information as possible.
For example, some of the people tested were still alive and were
available for retesting to access how intelligence might have evolved over time. Intelligence turned out to be an enduring
attribute.
“…the people who had gotten
relatively low scores in 1932 tended to get relatively low scores in 1998, while
the high scoring children tended to score high in old age. If you had looked at the score of one of the
eleven-year-olds in 1933, you’d have been able to make a pretty good prediction
of their score almost seven decades later.”
These results suggested that an early intelligence test
might be useful in predicting performance in later life. Zimmer tells us that numerous investigators
attempted to look for such correlations.
“The US Air Force found that the
variation in g [general intelligence] among its pilots could predict virtually
all the variation in tests of their work performance. While intelligence tests don’t predict how
likely people are to take up smoking, they do predict how likely they are to
quit. In a study of one million people
in Sweden, scientists found that people with lower intelligence test scores
were more likely to get into accidents.”
These results suggest that general intelligence is something
that is deeply rooted and affects many aspects of our lives. The Scottish data further supported this viewpoint
when it was discovered that there was a relationship between longevity and
intelligence. The more intelligent
people tended to live longer.
“…Deary’s research raises the
possibility that the roots of intelligence dig even deeper. When he and his colleagues started examining
Scottish test takers in the late 1990s, many had already died. Studying the records of 2,230 of the
students, they found that the ones who had died by 1997 had on average a lower
test score than the ones who were still alive.
About 70 percent of the women who scored in the top quarter were still
alive, while only 45 percent of the women in the bottom quarter were. Men had a similar split.”
“Children who scored higher, in
other words, tended to live longer. Each
extra 15 IQ points, researchers have since found, translates into a 24 percent
drop in the risk of death.”
The second wave of Scottish youths tested in 1947 provided
more easily accessible data on life outcomes and allowed for a far greater
numbers of people to be tracked.
“As before, the researchers
found that lower intelligence test scores raised people’s risk of death. But when they broke down the deaths into
major causes, they found the same rule held true across the board. The people who scored in the to 10 percent
were two-thirds less likely to have died from respiratory disease than those in
the bottom 10 percent. They were half as
likely to have died from heart disease, stroke, and digestive diseases.”
The possible explanations for these results include the
factors mentioned above for explaining longevity being greater for the wealthy:
access to better healthcare (assuming they earned more income), and greater
wisdom in lifestyle choices. Some people
don’t find these explanations compelling.
The researcher, Ian Deary, believes these correlations suggest an
intimate correlation between exceptional brain function and exceptional body
function.
“But the influence of
intelligence on longevity is so broad that Deary has proposed a deeper
connection. Scores on intelligence tests
may gauge some broad feature of human biology, in the same way a thermometer or
blood pressure reading does. The
efficiency in the brain may have something in common with how well other parts
of the body run. And this ‘system
integrity,’ as Deary calls it, may help determine how long the whole system
runs before falling apart.”
Zimmer remains neutral on this hypothesis, but he does
provide some information that suggests that a well-functioning brain might be
an indicator of a well-functioning body.
“Our brains use 84 percent of
our twenty-thousand-odd protein coding genes.”
We have encountered two sets of data. One indicates that wealth improves longevity,
the other indicates that intelligence improves longevity. The two can be in agreement if attaining a
high income is correlated with intelligence.
It is not difficult to expect such a tendancy to exist. It is also not difficult to expect a
correlation between a well-functioning intelligent brain and exceptional physical
performance such as required in athletics (or piloting a lane or avoiding
having accidents). The notion presented
by Deary that intelligence is an indicator of “system integrity” is intriguing,
but difficult to evaluate because it depends on biology at an extremely deep
level. But wouldn’t it be fascinating if
it were true?
The interested reader might find the following articles
informative:
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