MUNICH, Germany, Aug. 30 (UPI) -- From Malaysia to Montana, the same risk factors -- smoking, high cholesterol, obesity and high blood pressure -- cause 90 percent of heart attacks, Canadian researchers reported.
Controlling those factors and five other major contributors could prevent nine out of 10 heart attacks, said Dr. Salim Yusuf, professor of medicine at McMaster University in Hamilton, Ontario.
The finding contradicts the long-held belief that risk factors only explain about half of all heart attacks, said Yusuf, who headed the largest-ever international study of heart disease risks.
Yusuf told United Press International he has "always doubted that 50 percent estimate."
He presented the new research Sunday at the European Society of Cardiology Congress 2004 in Munich and will publish it later this week in the British journal The Lancet.
The study by Yusuf and colleagues included 15,152 people who has suffered a first heart attack, plus 14,820 healthy volunteers who were matched for age, race and gender. The study subjects came from 52 countries "in every populated continent of the world," he said.
The subjects included 7,000 participants of European extraction, 2,000 from Latin America, 6,000 from China, 4,000 from South Asia, 3,500 from Arab nations, 2,000 from other parts of Asia and 1,400 from Africa.
In addition to its large size, the study is notable because it uses two new approaches to measure heart attack risks. Rather than using the standard obesity calculation of body-mass index, or BMI, the study used waist circumference, which is a direct gauge of abdominal fat -- the type of fat most likely to cause a heart attack. A waist measurement of more than 31.5 inches (80 centimeters) in women and more than 33.5 inches (85 cm) in men is associated with increased risk of heart attack, Yusuf said.
In place of the standard blood test for cholesterol -- which requires at least a 12-hour fast and then lists the so-called good and bad cholesterol, as well as total cholesterol -- the study used a new, simple blood test that measured the ratio between small and large cholesterol molecules.
This method, which does not require fasting, measures the ratio between apoliprotein B and apoliprotein A-1.
"I call it the ratio of nasty vs. good molecules," Yusuf said. The nasty molecules are small and dense while the good are larger and more diffuse. He said a ratio "below 0.5 is normal, 0.5-0.75 is moderate risk, 0.75 to 1.0 is high risk and higher than 1.0 is very high risk."
Persons in the highest risk for the Apo B/Apo A-1 ratio suffered a 54 percent increased risk of heart attack, he said.
Smoking by itself increased heart attack risk by 36 percent, but when combined with an excessive Apo ratio, the two factors "account for about two-thirds of all heart attacks," he said.
Even a little puff is dangerous. Smoking one to five cigarettes a day increases heart attack risk by 40 percent compared to non-smokers. Smoking 20 cigarettes a day -- one pack -- is associated with a four-fold increased risk and smoking two or more packs a day "is associated with a nine-fold increased risk," Yusuf said.
A daily aspirin is associated with reduced heart attack risk, but "smoking three cigarettes can wipe out the protective effect of aspirin and wipe out two-thirds of the protective effect of (lipid-lowering drugs)," he said.
Calling the study the "most important work of my life," Yusuf told conference attendees the power of some risk factors was surprising.
For example, he noted stress -- which he previously had considered a "soft" risk factor -- actually doubled heart attack risk. The study suggests stress is most dangerous when it is characterized as "permanent," or when it is constant, whether at home or at work. Moreover, people who say they have little control on the job or in the home are more likely to suffer stress-related heart disease.
Rounding out the list of risk factors were diabetes, high blood pressure, sedentary life style and a diet that does not include generous servings of fruits and vegetables. On the positive side, a good diet, regular exercise and moderate alcohol intake reduced the risk of heart disease -- regardless of race or ethnicity.
Dr. Robert Horton, editor of The Lancet, told UPI the study demonstrates the potential for real health benefits that can be achieved without pills or surgery.
Horton, who often has been critical of the pharmaceutical industry, said the results indicate the need for "political action. I think it is really time to consider political moves to control the food industry."
Among the possible options, he suggested, would be special taxes on foods known to contribute to obesity or limits on where such foods could be sold.
The study received funding from 39 institutions, including the Canadian Institutes of Health Research and the Heart and Stroke Foundation of Ontario, as well as a number of pharmaceutical companies.
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Peggy Peck covers research and health issues for UPI Science News. E-mail [email protected]
