INTELLIGENCE is one of the biggest risk factors in predicting whether someone will suffer heart disease or stroke.
Researchers have found that lower IQ scores are linked to an increased risk of cardiovascular disease (CVD). But previously it has not been clear how strongly IQ could be used to predict someone's chances of developing the disease compared with other well-known factors such as obesity and high blood pressure.
Now, a large Scottish study, funded by the Medical Research Council, has found that a lower intelligence score is second only to smoking as a predictor of CVD. The analysis was based on data collected in 1987 in a cohort of 1,145 men and women aged about 55 and followed up for 20 years.
Researchers collected information about height, weight, blood pressure, smoking habits, physical activity, education and occupation. IQ was assessed using a standard test.
When all the data was compared, smoking was found to be the most important indicator of heart problems. But this was followed by low IQ, ahead of other risk factors such as high blood pressure and lack of exercise.
The researchers said there were "a number of plausible mechanisms" that could explain why lower IQ scores raised the risk of CVD, which covers all diseases involving the heart and circulation. One explanation might be that high IQ makes people more likely to take healthy decisions, such as not smoking and taking exercise. In turn, this leads to lower rates of obesity and blood pressure.
Lead researcher Dr David Batty, of the MRC Public Health Science Unit in Glasgow, said that the individual skills reflected in a person's IQ may be important in the management of personal cardiovascular risk.
"From a public health perspective, there is the possibility that IQ can be increased, with some mixed results from trials of early learning and school readiness programmes," he said.
"It may also be worthwhile for health campaigns to be planned with consideration of individual cognition levels."
Fotini Rozakeas, a cardiac nurse for the British heart Foundation, said: "This study shows that IQ may be a factor in determining vulnerability to heart and circulatory disease, particularly in lower socioeconomic groups.
"However, heart disease is largely preventable and many of the risk factors the study considered, such as smoking, physical inactivity and high blood pressure, are ones we can all do something about."
The findings, published in the European Journal of Cardiovascular Prevention and Rehabilitation, come from the West of Scotland Twenty-07 Study, which was designed to investigate the influence of social factors on health.