Having a lower than average IQ is in itself a risk factor for heart disease, according to a new study by UK researchers.
In the study of over 4,000 people, Dr David Batty and his colleagues at the University of Glasgow and the University of Edinburgh found that IQ alone explained more than 20 percent of the difference in mortality between high and low socio-economic groups.
The researchers found that the results were the same even when known heart disease risk factors were taken into account.
"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," the BBC quoted Dr David Batty, who led the research for the Wellcome Trust and the Medical Research Council, a saying.
"Environmental exposures and health-related behaviours, such as smoking, diet and physical activity, can explain some of this difference, but not all of it," he added.
The research team studied a group of 4,289 former US soldiers from all walks of life.
As expected from past trends, those on low incomes and with less education had a higher risk of dying from cardiovascular disease.
However, when the researchers took into account intelligence or cognitive function, commonly referred to as IQ, and controlled for nine other known heart disease risk factors, IQ alone explained 23 percent of the differences in mortality between the highest and lowest socio-economic groups in the study.
They offer several possible explanations for this - low IQ scores might simply be a marker of underlying poor health or intelligence might lead to greater knowledge about how to keep healthy.
Batty said, whatever the explanation, the findings imply the IQ of the public should be considered more carefully when preparing health promotion campaigns.
"I think the public health messages on things like diet, exercise and smoking could be simplified," Batty said.
"For instance, we often read about how some types of alcohol are good for you while others, or even the same ones, are not. The messages can be difficult to interpret, even by knowledgeable people," he added.
The study has been published in the European Heart Journal.