High cholesterol and coronary artery disease
What is high cholesterol?
High cholesterol is an excess of cholesterol in your blood. Cholesterol is a type of lipid, which is a group of fats and fat-like substances found in your body and in the foods you eat. A high cholesterol level is often due to a problem with your lipoproteins (low-density lipoproteins, or LDL, and high-density lipoproteins, or HDL), which are combinations of cholesterol, fat, and protein that your body uses to transport cholesterol and fat nutrients in your blood. The other important lipid nutrient that your body processes and distributes along with cholesterol is triglyceride, a fat nutrient that your muscle cells use for energy and that your body stores in your fat tissue for later use.
Why is high cholesterol a risk factor for coronary artery disease?
An imbalance of these cholesterol-carrying lipoproteins can lead to a buildup of cholesterol inside your arteries. Although doctors do not completely understand the process, this excess cholesterol gets deposited in the walls of your arteries, which contributes to the development of coronary artery disease (CAD). The hard plaque that forms in your arteries as a result of atherosclerosis is made largely of cholesterol.
Cholesterol is measured in millimoles per litre (mmol/L) or milligrams per decilitre (mg/dL). A desirable cholesterol level also includes a balance of the different forms of cholesterol. The following cholesterol levels are recommended by Canadian experts for those without CAD and those at low, moderate, or high risk of having CAD:1, 2
Low-density lipoprotein (LDL)
LDL carries cholesterol from the liver to other parts of the body where it is needed for cell repair and other activities. However, under certain conditions, LDL cholesterol builds up in the walls of the arteries. For this reason, LDL cholesterol is often referred to as "bad" cholesterol. In general, cholesterol-lowering efforts are most often aimed at reducing levels of LDL cholesterol to reduce the risk of atherosclerosis, heart attack, and other complications.
- If you are at a low risk for complications of high cholesterol (you do not have conditions such as coronary artery disease [CAD], diabetes, or obesity), an LDL cholesterol level of less than 5.0 mmol/L (195 mg/dL) and a total cholesterol to HDL ratio of less than 6.0 is normal.
- If you are at a moderate risk for complications of high cholesterol, an LDL cholesterol level of less than 3.5 mmol/L (135 mg/dL) and a total cholesterol to HDL ratio of less than 5.0 is normal.
- If you are at a high risk for complications of high cholesterol, an LDL cholesterol level of less than 2.0 mmol/L (80 mg/dL) and a total cholesterol to HDL ratio of less than 4.0 is normal.
- If you have diabetes, an LDL cohlesterol level of less than 2.0 mmol/L (80 mg/dL) is normal.3
High-density lipoprotein (HDL)
HDL cholesterol is often referred to as "good" cholesterol because it helps remove excess "bad" (LDL) cholesterol from the body. HDL cholesterol picks up leftover cholesterol from the bloodstream and carries it to the liver for disposal. Low HDL cholesterol increases the risk of coronary artery disease, and high levels of HDL cholesterol appear to help protect against heart disease. If you are at risk for heart disease, it may be beneficial to raise your HDL cholesterol levels.
An HDL level that is:
- 1.5 mmol/L (60 mg/dL) or higher is desirable. It reduces the risk of heart disease, even if total or LDL cholesterol is high.
- Between 1.0 to 1.5 mmol/L (40 to 60 mg/dL) is considered acceptable.
- Below 1.0 mmol/L (40 mg/dL) is considered low. Low HDL is considered a major risk factor for coronary artery disease in people who also have high total cholesterol levels.
Triglycerides
Triglycerides are another form of fat found in the blood. High triglyceride levels may contribute to fat buildup in the heart arteries and increase the risk of developing coronary artery disease (CAD).
The following are general triglyceride guideline levels. A triglyceride level of:
- Less than 1.7 mmol/L is considered desirable.
- 1.7 to 6.0 mmol/L is considered moderately high.
- 6.0 mmol/L or greater is considered severe hypertriglyceridemia.
Lowering LDL and total cholesterol levels can help lower the risk of CAD, as well as heart attack, stroke, and death, in many people with average to high cholesterol levels. People at high risk for CAD are especially encouraged to keep their cholesterol levels low.4
For more information, see the topic High Cholesterol.
| Author: | Douglas Dana Robin Parks, MS | Last Updated: September 21, 2007 |
| Medical Review: | Anne C. Poinier, MD - Internal Medicine Caroline S. Rhoads, MD - Internal Medicine Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology Robert A. Kloner, MD, PhD - Cardiology Ruth Schneider, MPH, RD - Diet and Nutrition | |
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