Previously, researchers thought that only about half of heart attacks were explained by risk factors such as smoking or cholesterol. But now they say that the cause of almost all heart attacks can be pinpointed to one or more of the following:
- Abnormal cholesterol
- High blood pressure
- Abdominal obesity
- Sedentary lifestyle
- Eating too few fruits and vegetables
- Abstaining from alcohol
These risk factors are equal-opportunity killers -- black or white, Asian or American, young or old, man or woman -- all can fall victim by these same risks. Diet, exercise, and moderate consumption of alcohol can decrease risk of heart disease, but cannot reverse the potential danger posed by risks such as high cholesterol or smoking, says Salim Yusuf, MD, who led the study.
Studies have shown that men who drink up to two alcohol drinks a day and women who drink up to one a day have a lower risk of heart disease. One drink is generally considered to be four to five ounces of wine, a 12-ounce beer, or 1 ounce of liquor.
The study included nearly 30,000 people -- half were first heart attack survivors and half were healthy volunteers of similar age, race, and gender to the heart attack patients. Since the study was conducted in 52 countries located on every populated continent, Yusuf tells WebMD that it is now possible to say that "the same risk factor that causes a heart attack in a white European will cause a heart attack in an Asian."
Bigger Waist, Bigger Risk
Rather than relying on body mass index (BMI), the researchers took waist measurements. A waist circumference of more than 80 centimeters (32 inches) in women and more than 85 centimeters (34 inches) in men increased risk. Yusuf says measuring the waist is a better predictor of heart attack risk because "it is a measure of abdominal fat, which is the type of fat that is most closely associated with heart attacks."
Bigger Cholesterol Is Better
Yusuf presented the study results at the European Society of Cardiology meeting. He says that cholesterol size also plays a role in determining risks. Smaller, denser cholesterol molecules increase the risk of heart disease; these can more easily invade the artery wall causing inflammation and atherosclerosis plaque. The higher the amounts of smaller and denser particles, the higher the risks relative to larger cholesterol particles.
He says that this factor alone may increase the risk of heart attacks by as much as 54%. Yet when a smoker has a bad lipid ratio (smaller to larger particles) "that combination accounts for two-thirds of heart disease."
In the study researchers measured particles which carry cholesterol in the blood called apoproteins. The ratio of apoliprotein B (which carries "bad" LDL cholesterol) and apoliprotein A-1 (which carries "good" HDL cholesterol) is a much simpler test, Yusuf says. "I call it the ratio of nasty versus good molecules."
People at the highest risk for the ApoB/Apo A-1 ratio increased their risk of heart attack by 54%, he said.
Heart Attack Risk Rises With One Cigarette
Second on the nine-item list is smoking which was associated with a 36% increased risk of heart attack. And Yusuf warns that risk increases with the first cigarette: smoking one to five cigarettes a day increases heart attack risk by 40% compared with nonsmokers. Smoking 20 cigarettes a day (one pack) is associated with a fourfold increased risk of heart attack and smoking two or more packs a day "is associated with a ninefold increased risk," he says.
Moreover, while a daily low-dose aspirin can protect the heart, "smoking three cigarettes can wipe out the protective effect of aspirin and wipe out two-thirds of the protective effect of [cholesterol-lowering drugs]," he says.
Stress Effect Stronger Than Thought
Calling the study the "most important work of my life," Yusuf says that the power of some risk factors was surprising. For example, he says that stress, which he previously considered a "soft" risk factor, actually doubled the risk of heart attack. The study indicates that stress is most dangerous when it is described as "permanent" and when stress 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 doesn't include generous servings of fruits and vegetables. On the positive side, a good diet, regular exercise, and moderate alcohol intake did reduce the risk of heart disease -- again the reduction was the same regardless of race or ethnicity.
Richard Horton, MD, editor of The Lancet, says that the study demonstrates the potential for real health benefits that can be achieved without pills or surgery. Horton says 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 would be special taxes on foods known to contribute to obesity or limits on where such foods can be sold. Horton was not involved in the study.
Yusuf agrees that a concerted, international effort could greatly reduce what he calls a pandemic of heart disease. "We need to build healthier environments," he says. "Shopping, work, and residence should be concentrated in the same area so that people can walk to a store or walk to work or school."
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.