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Scientists link low IQ with heart disease risk
A unique study looking at the difference in cardiovascular disease (heart
disease and stroke) and life expectancy between people of high and low
socio-economic status has found that a person’s IQ may have a role to play.
Authors of the study published in Europe’s leading cardiology journal, the
European Heart Journal on Wednesday 15 July, analysed data from a group of 4,289
former soldiers in the USA. They found that IQ explained more than 20% of the
difference in mortality between people from socio-economically disadvantaged
backgrounds compared to those from more advantaged backgrounds. Importantly,
this was in addition to the classical, known risk factors for heart disease,
such as smoking and obesity.
Dr David Batty, who led the research, said: “We already know that
socio-economically disadvantaged people have worse health and tend to die
earlier from conditions such as heart disease, cancer and accidents.
Environmental exposures and health-related behaviours, such as smoking, diet and
physical activity, can explain some of this difference, but not all of it. This
raises the possibility that, as yet, unmeasured psychological factors need to be
considered. One of these is intelligence or cognitive function, commonly
referred to as IQ. This measures a person’s ability to reason and problem solve.
IQ is strongly related to socio-economic status.”
Dr Batty, an epidemiologist and Wellcome Trust Research Fellow at the Medical
Research Council’s Social and Public Health Sciences Unit, University of Glasgow
(UK), and at the MRC Centre for Cognitive Ageing and Cognitive Epidemiology,
University of Edinburgh (UK), and his colleagues were able to look at the
relationships between IQ, socio-economic status and heart disease in the study
of US former soldiers because, unusually, this group had this detailed
information.
“We wanted to know what is it about low socio-economic status that gives you
a higher risk of cardiovascular disease,” explained Dr Batty. “In other words,
how is socio-economic adversity getting ‘under the skin’ to cause people to have
a reduced life expectancy or increased risk of cardiovascular disease? This is
important to know so that we can actually try to do something about the
problem.”
Dr Batty found that, as expected, people on low incomes (in both early and
mid-life), in jobs with low prestige and with less education, had an
approximately two to seven-fold higher risk of dying from all causes and
cardiovascular disease than people of a higher socio-economic status. “This
confirmed what we already knew,” he said. “However, when we took into account
IQ, we found this explained approximately 50% of that difference.”
A second analysis showed that taking into account nine known risk factors for
heart disease (such as smoking and obesity) explained about 40% of the
difference. The final analysis that adjusted for all three (age, known risk
factors and IQ) explained between 63-65% of the difference in deaths from all
causes and heart disease between people with high and low socio-economic status.
“The difference between the second and third analyses showed that IQ alone
explained a further 23% of the differences in mortality between the higher and
lower ends of the socio-economic spectrum, in addition to the other, known risk
factors,” said Dr Batty. “IQ wasn’t a magic bullet in this study, but this
psychological variable had additional explanatory power on top of the classic
variables such as smoking, high blood pressure, high blood glucose and obesity.
It has partially explained the differences in death from heart disease and all
causes.”
Commenting on the public health implications of his study, Dr Batty and his
colleagues write: “Our findings suggest that measured IQ does not completely
account for observed inequalities in health, but, probably through a variety of
mechanisms, may quite strongly contribute to them. This implies that efforts to
reduce inequalities should continue to be broadly based, including educational
opportunities and interventions directed at early life. . . . It may be that
individual cognition levels should be considered more carefully when preparing
health promotion campaigns and in the health professional–client interaction.”
Dr Batty said: “I think the public health messages on things like diet,
exercise and smoking could be simplified. At present, the messages can be quite
complicated, even contradictory, and they lack clarity. For instance, we often
read about how some types of alcohol are good for you while others, or even the
same ones, are not. These messages can be difficult to interpret, even by
knowledgeable people.
“Secondly, efforts to reduce socio-economic inequalities should continue on a
broad front. Initiatives aimed at raising living standards and education of the
most disadvantaged families with children could potentially make a difference to
those children’s health and well-being in later life.” - ESC Press
More information:
 “Does
IQ explain socio-economic differentials in total and cardiovascular disease
mortality? Comparison with the explanatory power of traditional cardiovascular
disease risk factors in the Vietnam Experience Study”. European Heart Journal.
doi:10.1093/eurheartj/ehp254.
http://www.escardio.org/
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