Recently, I saw a new patient in my office who asked me questions very similar to the questions above. She was a 46-year-old woman in fairly good health. She came to see me because her father had suffered a heart attack a few weeks before; at that time he had also been diagnosed with high cholesterol (hypercholesterolemia). My patient wanted to know if her father's high cholesterol and penchant for junk food had caused his heart attack. She was also very anxious about whether this meant that she, too, was likely to have hypercholesterolemia and she wanted to be tested right away. However, she wasn't really sure what cholesterol was or how it related to heart disease, so I started with the basics.
What is Hypercholesterolemia?
Hypercholesterolemia is an excess of cholesterol, a fat-related substance, in the blood. It may also be referred to as hyperlipidemia or dyslipidemia (lipids are a group of fat-like substances that include cholesterol and triglycerides).
Why is Hypercholesterolemia Important?
Approximately 60 million Americans have hypercholesterolemia. While this fact in itself may not be frightening, it is important to realize that high cholesterol is a major risk factor for atherosclerotic heart disease (narrowed arteries due to cholesterol plaque buildup), which is the leading cause of death and disability in the Western hemisphere. More than 13 million people in this country alone have coronary artery disease; about 500,000 people die from heart disease each year. For these reasons, we focus a great deal of attention on diagnosing and treating high cholesterol; it is an effective way to prevent people from developing and dying from atherosclerotic heart disease. People of any age can have hypercholesterolemia, but it is most commonly diagnosed in the fifth through seventh decade of life.
What Causes Hypercholesterolemia?
Most cases of hypercholesterolemia are caused by a combination of genetics and diet. A diet which contains foods that are rich in fat and cholesterol can contribute to the development of hypercholesterolemia. These foods include red meat, fried chicken, whole milk, egg yolks, butter, ice cream, and pastry. The genes involved in hypercholesterolemia are usually multiple; however, a small percentage of people (less than five percent) with hyperlipidemia have a defect in a single gene that results in a hereditary disorder of lipid metabolism. The two most common types of these disorders are familial hypercholesterolemia, in which the cholesterol is elevated, and familial combined hyperlipidemia, in which both the cholesterol and triglycerides are elevated. Both these conditions are related to the onset of heart attacks and other symptoms of atherosclerotic heart disease at an early age. Hyperlipidemia can also occur as a result of other medical conditions, such as diabetes mellitus, hypothyroidism, liver disease, alcoholism, and certain types of kidney disease. Various medications, including estrogen, steroids, and certain blood pressure drugs can cause hyperlipidemia as well
What are "Good" and "Bad" Cholesterol?
Dietary fat is naturally absorbed from the small intestine into the bloodstream, where it is broken down and packaged for transport by binding to special proteins, called lipoproteins. There are different types of lipoproteins that carry cholesterol in the blood; the two most famous types are low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL cholesterol is nicknamed "bad cholesterol" because it delivers cholesterol to the walls of blood vessels and is associated with atherosclerosis. HDL cholesterol is called "good cholesterol" because it is targeted to other organs, like the liver, where it is used in making substances that the body needs. This is really an oversimplification; actually, there are different phenotypes (or subtypes) within each class of lipoprotein that make it more or less likely to cause atherosclerosis. However, thinking of good and bad cholesterol in this way can be useful.
How is Cholesterol Related to Heart Disease?
Coronary artery disease (CAD), which is the cause of heart attacks and angina (chest pain associated with blocked coronary arteries), develops partly as a result of cholesterol deposition in the coronary arteries (the blood vessels that supply blood to the heart). This process leads to the formation of atheroscleroticplaques, which can reduce blood flow to the heart and cause angina. If one of these plaques ruptures, the blood supply to a portion of the heart may be blocked entirely, and a heart attack ensues.
Numerous studies have demonstrated a strong link between coronary artery disease and hypercholesterolemia. Specifically, high levels of LDL-cholesterol and low levels of HDL-cholesterol are associated with a significantly increased risk of CAD. Put another way, people with high LDL levels have a much higher risk of having a coronary event than do people with normal levels. In contrast, a high HDL level is protective against CAD.
What are the Desirable Levels of Cholesterol?
The cholesterol levels that are considered desirable vary, depending on whether or not you have coronary artery disease or risk factors for CAD. These risk factors include your age, older than 45 for men and older than 55 for women, postmenopausal status (without hormone replacement therapy), significant family history of CAD, cigarette smoking, hypertension, and diabetes.
In healthy adults without CAD or diabetes, a total cholesterol level less than 200 mg/dl, an LDL level less than 130 mg/dl, and an HDL level greater than or equal to 60 mg/dl are desirable. Borderline levels are a total cholesterol of 200 to 239 mg/dl, an LDL level of 130 to 139, and an HDL level of 35 to 59 mg/dl. A total cholesterol level greater than or equal to 240 mg/dl, an LDL level greater than or equal to 160, and an HDL level less than 35mg/dl are considered undesirable. These are levels that you can use to direct your efforts in lowering your cardiac risk.
What About Triglycerides?
Although we tend to focus on LDL- and HDL-cholesterol, other lipid components are also important. These include triglycerides (a building molecule of fats) and the triglyceride-rich lipoproteins: very low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL). As with cholesterol, a high triglyceride level is usually the result of a person's diet and genetic makeup, but it can also be caused by other conditions, such as diabetes and hypothyroidism, and by some medications. The relationship between triglycerides and atherosclerosis is not as well established as it is for cholesterol. What we do know is that hypertriglyceridemia is linked to other CAD risk factors, such as low HDL level and central (apple-shaped) obesity. The desirable level of triglycerides in healthy adults is less than 200 mg/dl.
Who Should Have Their Cholesterol Checked?
Virtually everyone should be screened for high cholesterol. Many physicians, including myself, follow the guidelines put forth by the National Cholesterol Education Program, which recommends that all individuals begin screening with total- and HDL-cholesterol levels at age 20 and continue to check their cholesterol levels at five-year intervals if they are normal. Other physicians favor a more targeted approach, and screen only those individuals who have other risk factors for CAD. Patients with established coronary artery disease, diabetes, familial hyperlipidemia, or other CAD risk factors should be tested more frequently, using a fasting lipid profile (this includes total, LDL and HDL cholesterol, and triglycerides).
What if My Cholesterol is High?
If your cholesterol is high, you should talk to your physician about your overall risk for CAD; this assessment will guide the intensity of treatment. Healthy people with hyperlipidemia can often reduce their cholesterol and triglycerides to desirable levels by diet and exercise alone. Others may require medication to lower their lipids. However, it is important to remember that lowering you cholesterol is part of a larger plan to reduce your risk of developing coronary artery disease and to foster a healthy lifestyle.
Let's return to the example of my new patient. She was interested in learning not just her cholesterol level but her overall risk for coronary artery disease. As I mentioned, she was in fairly good health. She had no history of hypertension, diabetes, or other chronic conditions. She never had chest pain or shortness of breath. She ate a well-balanced diet for the most part, but had frequent cravings for chocolate cake and ice cream which she could not resist. She also smoked about a half-pack of cigarettes per day since the age of 18.
I checked my patient's lipid levels that afternoon. She had a total cholesterol of 248, with an LDL of 162, an HDL of 36, and a triglyceride level more than 250. Because she was post-menopausal and a smoker, she had at least two other risk factors for CAD. We talked about several ways she could not only lower her cholesterol, but reduce her overall cardiac risk and feel healthier too. She was actually quite relieved to know that there were many things she could do to achieve these goals. For example, reducing the fat in her diet, exercising, and enrolling in a smoking cessation program. I also told her that medication would be a future option.
Summary
Hypercholesterolemia is an excess of cholesterol in the blood. High levels of LDL cholesterol are associated with a significantly higher risk of coronary artery disease (CAD). Low HDL cholesterol is also associated with an increased risk of CAD. The desirable cholesterol levels for healthy, asymptomatic adults are a total cholesterol less than 200 mg/dl, LDL less than 130 mg/dl, and HDL greater than or equal to 60 mg/dl. For those with coronary artery disease or diabetes, the guidelines are more stringent. I recommend that all healthy adults have their cholesterol checked every five years, starting at age 20. If you have diabetes, coronary artery disease, or a family history of premature CAD or hyperlipidemia, you should check your cholesterol more often. If your cholesterol is high, talk to your doctor about the various treatment options that would be appropriate for you.
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