Vast majority of heart attacks may be predicted by nine easily measurable factors

A major Canadian-led global study has found that the vast majority of heart attacks may be predicted by nine easily measurable factors and that these factors are the same in virtually every region and ethnic group worldwide.

The INTERHEART study looked at more than 29,000 people in 52 countries and from all inhabited continents of the world. The study was presented Aug. 29 at the European Society of Cardiology (ESC) Congress in Munich, Germany by Dr. Salim Yusuf, a professor of medicine at the Michael G. DeGroote School of Medicine at McMaster University in Hamilton, Ontario, Canada and director of the Population Health Research Institute at McMaster University and Hamilton Health Sciences, which coordinated the study.

The study found that the two most important risk factors are cigarette smoking and an abnormal ratio of blood lipids (Apolipoprotein B/Apolipoprotein A-1), which together predicted two-thirds of the global risk of heart attack. Additional risk factors are high blood pressure, diabetes, abdominal obesity, stress, a lack of daily consumption of fruits and vegetables and a lack of daily exercise. Regular consumption of small amounts of alcohol was also found to be modestly protective. Worldwide, these nine factors collectively predict more than 90 per cent of the risk of a heart attack.

The INTERHEART study, one of the largest case control studies examining the importance of heart disease risk factors, involved 15,152 individuals with their first heart attack and 14,820 others who did not have heart disease but who were of the same age, gender, and from the same city. The study was funded by the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario and 37 other funding sources, including unrestricted support from several pharmaceutical companies.

This major study is the first examination of whether risk factors for heart attack have a similar or different impact in all major ethnic groups and major areas of the world. It included 7,000 people of European extraction; 2,000 from Latin America, 6,000 Chinese; 4,000 South Asians; 2,000 from other parts of Asia; 3,500 Arabs and 1,400 Africans. There were 450 Canadians included.

Yusuf said conventional wisdom had previously suggested that only half of the risks of heart attacks may be foreseen, but the INTERHEART findings mean the overwhelming majority of heart attack risk may be predicted.

“These risk factors appear to predict the majority of the risk in virtually every region, every ethnic group, in men and women and in the old and the young,” said Yusuf. “This suggests that the message of preventing cardiovascular disease can be quite simple and, generally, similar across the world, after taking into account economic and cultural differences.

“Since these risk factors may all be modified, this is remarkable and will change the way we look at heart attack prevention. It means we should be able to prevent the majority of premature heart attacks in the world.”

Dr. Alan Bernstein, president of the Canadian Institutes of Health Research, pointed out that worldwide there is a growing epidemic of cardiovascular disease with more than 15 million deaths from heart attacks in 1998 alone.

“This is a landmark study. It suggests that a combination of lifestyle changes including stopping smoking, eating a healthier diet and exercising could lead to an 80 per cent reduction in the risk of heart attacks," he said. "The INTERHEART study provides the health research evidence needed to build national and international programs for the prevention and control of one the leading cause of death in Canada and world-wide."

The INTERHEART study is scheduled to be published in the prestigious medical journal The Lancet on Sept. 11, 2004 but will be available on its website at www.thelancet.com on Friday, September 3.

That issue will also include a second article from the study on the factor of stress as a risk attribute for heart attacks. It found that various simple measures of patient stress and psychosocial status were able to predict the risk of heart attacks, said its lead author, Dr. Annika Rosengren, professor of cardiology at Goeteborg University, Sweden.

“Collectively, these were responsible for about one-third of the risk in the population studied,” said Rosengren.

Dr. John Kelton, dean of the Michael G. DeGroote School of Medicine and dean and vice-president, Faculty of Health Sciences, McMaster University, said: “The results of this massive study will change public health policy around the world. Different countries will be able to pinpoint risk factors for their people and address the root causes of heart disease.”

The INTERHEART study was endorsed by the World Health Organization, the World Heart Federation, and the International Clinical Epidemiology Network.