Cause of Most Heart Attacks Found
Researchers Say They May Know What Causes 90% of 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.