November 11, 2005

High IQ in childhood tied to longer life

By Amy Norton

NEW YORK (Reuters Health) - Smarter children may enjoy
longer lives, the results of a new study suggest.

The study, which followed elderly adults deemed gifted by
childhood IQ tests, found that the higher their early IQs were,
the longer they lived -- up to a point, at least. The survival
advantage began to plateau after a childhood IQ of 163, an
intelligence level few people reach.

Dr. Laurie T. Martin and Laura D. Kubzansky of the Harvard
School of Public Health report these findings in the American
Journal of Epidemiology.

Though the reasons for the link between IQ and longevity
are not clear, it does not appear to be merely a reflection of
income and social position. As children, the participants were
from affluent families and most were white. Yet childhood IQ
was still a factor in their lifespan.

Similarly, in an earlier study of Americans with more
varied childhood IQs and family incomes, Martin found that IQ
was related to health problems independently of socioeconomics.

This, she told Reuters Health, suggests that IQ affects
longevity among lower-income people as well.

As research has already linked IQ to mortality, the current
study, according to Martin, was in part an attempt to see how
far the IQ-health advantage extends. The researchers expected
there to be a cutoff at which a high IQ no longer brought any
extra health benefits.

And there was. But, Martin said, they were surprised at how
high that cutoff turned out to be.

IQs of 163 or higher are not often seen; the average IQ
score in the general population is 100 (by definition), and
children who score above 130 are considered "gifted."

The current study is based on data from 862 men and women
followed since childhood, starting in 1922, until 1986. All had
childhood IQs of 135 or higher, with the average being 151.

The researchers found that, up to the cutoff point of 163,
participants' risk of dying during a given period decreased as
their IQ increased; for example, those with a childhood IQ of
150 had a 44 percent lower risk of death than those with an IQ
of 135.

Though it's not clear why childhood IQ itself might affect
a person's lifetime health, Martin and Kubzansky point to
several possibilities. For one, these children may be more
likely to take up healthy habits like regular exercise, while
shunning health risks like smoking. They are also more likely
to get high-paying, prominent jobs as adults, with all the
advantages that confers.

And in general, Martin noted, IQ scores reflect a "set of
skills," like reasoning, planning and communication, that
affect how people manage their health -- from talking with
their doctors to dealing with a complex healthcare system.

Understanding exactly why IQ affects longevity, according
to Martin, could ultimately help improve health and healthcare
for everyone.

SOURCE: American Journal of Epidemiology, November 2005.