Intelligence is second only to smoking as a predictor of heart disease, scientists say, suggesting public health campaigns may need to be designed for people with lower IQs if they are to work.

Research by Britain's Medical Research Council (MRC) found that lower intelligence quotient scores were associated with higher rates of heart disease and death, and were more important indicators than any other risk factors except smoking.

Heart disease is the leading killer of men and women in Europe, the United States and most industrialised countries.

According to the World Health Organisation, cardiovascular diseases and diabetes accounted for 32 per cent of all deaths around the world in 2005.

It is well known that people with poorer education and lower incomes often face higher risks of ill health and a range of diseases.

Studies have pointed to many likely reasons, including limited access to health care and other resources, poorer living conditions, chronic stress and higher rates of lifestyle risk factors like smoking.

The MRC study, which analysed data from 1,145 men and women aged around 55 and followed up for 20 years, rated the top five heart disease risk factors as cigarette smoking, IQ, low income, high blood pressure and low physical activity.

The researchers, led by David Batty, said there were "a number of plausible mechanisms" which might explain why lower IQ scores could raise the risk of heart disease, in particular a person's approach to "healthy behaviour".

Those who ignored or failed to understand advice about the risks of smoking or benefits of good diet and exercise for heart health would be more likely to be at higher risk, they wrote in the European Journal of Cardiovascular Prevention.

Mr Batty said it was important to recognise the public health implications of the findings; that skills reflected in a person's IQ may be important for managing heart disease 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 programs," he said.

The British Heart Foundation (BHF) advocacy group said better food labels with a simple-to-read colour code for high, medium and low-risk foods would give shoppers "at-a-glance information" and help them make healthier choices.

"To make real progress on tackling health inequalities, we need health promotion campaigns designed to reach everyone in the community," said Fotini Rozakeas, a BHF cardiac nurse.

- Reuters