Another important step in reducing your risk of a heart attack is to control your blood levels of LDL cholesterol, HDL cholesterol, and triglycerides. Some people are able to do this with lifestyle changes—consuming a low-saturated-fat, low-cholesterol diet, exercising, and losing weight—but others require medication. The government's National Cholesterol Education Program has determined the levels of LDL cholesterol, HDL cholesterol, and triglycerides you should aim for to reduce your risk of a heart attack.
Total and LDL cholesterol levels
High levels of total and LDL cholesterol boost your risk of a heart attack because they are an indication of a greater likelihood that cholesterol will be deposited within the artery walls. Your total cholesterol level should be less than 200 mg/dL. However, close to half of Americans have levels of 200 mg/dL or higher. Studies show that a 10% decline (for example, from 220 mg/dL to 198 mg/dL) can decrease the risk of a heart attack by 20 to 30%.
More important than total cholesterol is your LDL cholesterol. How low your LDL cholesterol level should be depends on your degree of heart attack risk. For example, if you're at very low risk, your LDL cholesterol can be as high as 160 mg/dL. However, if you are at high risk (have had a heart attack or stroke or have diabetes or peripheral arterial disease, for example), your LDL cholesterol levels should be much lower—less than 100 mg/dL and, if possible, less than 70 mg/dL. Both total and LDL cholesterol levels can be reduced through lifestyle changes and, if necessary, cholesterol-lowering medications. Overall, the lower you keep your LDL cholesterol, the better your odds of avoiding a heart attack or stroke.
HDL Cholesterol Levels
Since HDL removes cholesterol from artery walls, a high—rather than a low—level helps protect against heart attacks. The National Cholesterol Education Program recommends an HDL cholesterol level of at least 60 mg/dL. An HDL cholesterol level below 40 mg/dL in men or less than 50 mg/dL in women is a risk factor for a heart attack. In fact, an LDL cholesterol level of less than 60 mg/dL may be associated with an increased risk of a heart attack if HDL cholesterol levels are below 40 mg/dL. HDL levels can be raised with lifestyle measures, such as weight loss, regular brisk exercise, quitting smoking, light consumption of alcohol, and certain cholesterol-lowering medications (if necessary).
Your goal for triglycerides is to keep them below 150 mg/dL. Triglyceride levels between 150 and 199 mg/dL are borderline high, levels between 200 and 499 mg/dL are high, and levels of 500 mg/dL or greater are very high. About one third of people have triglyceride levels above 150 mg/dL.
The risk of elevated triglycerides is especially great when combined with low levels of HDL cholesterol and small, dense LDL particles (see below). This pattern is common in individuals who are obese or have diabetes or prediabetes (fasting blood glucose levels of 100 to 125 mg/dL). Elevated triglycerides pose an especially high risk in individuals who have a high ratio of LDL to HDL cholesterol or when elevated triglycerides are associated with certain inherited conditions like dysbetalipoproteinemia (a genetic defect that causes high cholesterol and triglyceride levels).
Elevated triglyceride levels may interfere with the widening of the coronary arteries during physical exertion and may increase the risk of blood clots. But if you lower your triglycerides by losing weight, controlling diabetes (if present), and taking lipid-lowering drugs (when necessary), HDL cholesterol levels may also rise and further reduce your risk of a heart attack.
Size and Density of LDL Particles
Not all LDL particles are the same size. Some are small and dense; others are large and fluffy. The small, dense LDL particles are the ones that you need to worry more about, especially if you have more of them than the large, fluffy kind. Men are more likely than women to have a preponderance of small, dense LDL particles, as are people with triglyceride levels above 150 mg/dL.
Small, dense LDL particles enter the artery walls more easily, are more prone to oxidation than the larger particles, and thus are more likely to contribute to atherosclerosis and increase the risk of a heart attack. Their presence is also linked to higher triglyceride and lower HDL cholesterol levels as well as to a greater total number of LDL particles. Nonetheless, routine testing for small, dense LDL particles is not recommended, as conventional lipid measurements and risk factors do just as well at predicting heart attack risk.