How does high cholesterol cause heart disease?

Elevated levels of the type of cholesterol called low-density lipids (LDL) have been strongly associated with the development of blockages in the arteries that supply the heart with blood. These blockages are called plaques. They are made up of fatty substances and calcium. These plaques are what cause heart attacks.

If you have high cholesterol, fatty substances build up in your blood vessels and arteries. This leads to a hardening of the arteries and decreased blood flow. Without as much blood flow, the heart has less oxygen. Low oxygen levels and blood circulation tend to cause heart diseases and conditions like atherosclerosis, heart attack, and stroke.

The nicknames "good" and "bad" cholesterol relate to risk factors for heart disease. High levels of high density lipoproteins (HDL), or "good" cholesterol, are linked to lower heart disease risk; high levels of low density lipoproteins (LDL), or "bad" cholesterol, are associated with higher heart disease risk. Remember, keep you HDL levels High and your LDL levels Low.

Coronary heart disease (CHD) appears to be directly related to the amount of lipids (fats and fat-like substances) in the blood. That's because atherosclerosis, a fatty buildup in the cells lining the walls of arteries—in this case, the coronary arteries to the heart itself—narrows the diameter of these blood vessels and decreases blood flow, sometimes to a critical point.

Cholesterol is the main culprit in this buildup. The problem occurs when you have a lot of the wrong kind of cholesterol—low-density lipoprotein (LDL) cholesterol—which can clog the arteries. If you have a lot of the healthy kind of cholesterol—high-density lipoprotein (HDL) cholesterol—it can make a big difference in your risk of heart disease. Because HDL rids the body of excess LDL, the ratio of total cholesterol to HDL is very important. The amount of HDL itself or the ratio of total cholesterol to HDL often is a better predictor of the likelihood of heart disease than total cholesterol alone. If HDL is low (less than 35 mg/dL) and the ratio is high, the risk of heart disease increases, even when total cholesterol is not that high. (As many as 20 percent of men who have CHD follow that pattern.) In older women (especially those taking estrogen), it is not uncommon to find high levels of cholesterol that are not associated with a higher risk of heart disease because levels of HDL are also high (60 mg/dL or higher). Experts have defined "borderline-high" cholesterol as 200-239 mg/dL and "high" cholesterol as 240 mg/dL or higher.