HYperlipidemia

INTRODUCTION

Hyperlipidemia refers to increased levels of lipids (fats) in the blood, including cholesterol and triglycerides. Although hyperlipidemia does not cause symptoms, it can significantly increase your risk of developing cardiovascular disease, including disease of blood vessels supplying the heart (coronary artery disease), brain (cerebrovascular disease), and limbs (peripheral vascular disease). These conditions can in turn lead to chest pain, heart attacks, strokes, and other problems. Because of these risks, treatment is often recommended for people with hyperlipidemia.

This topic reviews the risk factors for coronary artery disease (sometimes called just “coronary disease”), the types of lipids, and when cholesterol testing should begin. The treatment of high cholesterol is discussed separately.

OTHER RISK FACTORS FOR CARDIOVASCULAR DISEASE

In addition to hyperlipidemia, there are a number of other factors that increase the risk of cardiovascular disease and its complications:

��Diabetes mellitus, type 1 and 2 .

��Hypertension (people with hypertension include those with a blood pressure at or above 140/90 and those who use blood pressure medication) .

��Cigarette smoking

��Family history of coronary disease at a young age in a parents or sibling (young, in this case, means younger than 55 for men and younger than 65 for women)

��Gender: Men have a higher risk of cardiovascular disease than women at every age

��Age: There is an increasing risk of cardiovascular disease with increasing age

LIPID TYPES

The term lipids includes cholesterol and triglycerides. There are many different types of lipid (also called lipoproteins). Blood tests can measure the level of your lipoproteins. The standard lipid blood tests include a measurement of total cholesterol, LDL (low density lipoproteins) and HDL (high density lipoproteins), and triglycerides.

Total cholesterol — A high total cholesterol level can increase your risk of cardiovascular disease. However, decisions about when to treat high cholesterol are usually based upon the level of LDL or HDL cholesterol, rather than the level of total cholesterol.

��A total cholesterol level of less than 200 mg/dL (5.17 mmol/L) is normal.

��A total cholesterol level of 200 to 239 mg/dL (5.17 to 6.18 mmol/L) is borderline high.

��A total cholesterol level greater than or equal to 240 mg/dL (6.21 mmol/L) is high.

The total cholesterol level can be measured any time of day. It is not necessary to fast (avoid eating for 12 hours) before testing.

LDL cholesterol — The low density lipoprotein (LDL) cholesterol (sometimes called "bad cholesterol") is a more accurate predictor of cardiovascular disease than total cholesterol. Higher LDL cholesterol levels increase your risk of cardiovascular disease.

Most healthcare providers prefer to measure LDL cholesterol after you have not eaten (fasted) for 12 to 14 hours. A test to measure LDL in people who have not fasted is also available, although the results may differ slightly.

Some healthcare providers make decisions about how to treat lipids based on a goal LDL cholesterol. If your healthcare provider uses this strategy, your goal LDL cholesterol will depend on several factors, including any history of cardiovascular disease and your risk of developing cardiovascular disease in the future (see 'Calculating risk' below). People at higher risk are often assigned a lower LDL cholesterol goal.

10-year risk of developing coronary artery disease

The 10-year risk score is based on information from the Framingham Heart Study, a large study that has followed participants, as well as their children and grandchildren, for greater than 50 years. The 10-year risk can be calculated for women (calculator 1) and for men (calculator 2).

Triglycerides — High triglyceride levels are also associated with an increased risk of cardiovascular disease, although this association is not typically important once other risk factors are taken into account. Triglyceride levels are divided as follows:

��Normal - less than 150 mg/dL (1.69 mmol/L)

��Borderline high - 150 to 199 mg/dL (1.69 to 2.25 mmol/L)

��High - 200 to 499 mg/dL (2.25 to 5.63 mmol/L)

��Very high - greater than 500 mg/dL (5.65 mmol/L)

Triglycerides should be measured after fasting for 12 to 14 hours.

HDL cholesterol — Not all cholesterol is bad. Elevated levels of HDL cholesterol actually lower the risk of cardiovascular disease. A level greater than or equal to 60 mg/dL or 1.55 mmol/L is excellent, while levels of HDL cholesterol less than 40 mg/dL or 1.03 mmol/L are lower than desired. There are no treatments for raising HDL cholesterol that has been proven to reduce the risk of heart attacks and strokes.

Similar to total cholesterol, the HDL-cholesterol can be measured on any blood specimen. It is not necessary to be fasting.

Non-HDL cholesterol — Non-HDL cholesterol is calculated by subtracting HDL cholesterol from total cholesterol. Since total cholesterol and HDL cholesterol can be measured without fasting, so can non-HDL cholesterol. Non-HDL cholesterol is a good predictor of cardiovascular risk and is a better predictor of risk than LDL cholesterol in people with type 2 diabetes and in women.

An appropriate non-HDL cholesterol goal can be calculated by adding 30 mg/dL (0.78 mmol/L) to your LDL cholesterol goal. As discussed, the LDL cholesterol goal depends on a number of factors. (See 'LDL cholesterol' above.)

CALCULATING RISK

Risk calculators are typically based on large studies of populations that are followed to see who develops cardiovascular disease. One such study, the Framingham Heart Study, has followed participants, as well as their children and grandchildren, for more than 50 years. Data from the Framingham Heart Study are used in the following .

WHEN SHOULD I HAVE MY CHOLESTEROL LEVEL TESTED?

Many expert groups have guidelines for cholesterol screening. The guidelines differ in their recommendations about when to start screening, how frequently you should be screened, and when to stop.

One expert group, the United States Preventive Services Task Force recommends the following:

��Lipid screening should start at age 35 in men without other risk factors for coronary artery disease and at age 20 to 35 in men with risk factors. These include men with:

•Diabetes

•A family history of heart disease in a close male relative younger than age 50 or a close female relative younger than age 60

•A family history of high cholesterol

•A personal history of multiple coronary disease risk factors (eg, smoking, high blood pressure).

��Lipid screening should definitely start at age 45 and perhaps at age 20 in women with risk factors for coronary disease. No recommendation for or against screening was made for women without risk factors for coronary disease. UpToDate authors believe that even low risk women should be screened starting at age 45.

��Those at risk for coronary disease should be treated based upon the results of their screening test.

��Screening should include total cholesterol and HDL-cholesterol levels and can be measured anytime (with or without fasting).

��The optimal time interval between screenings is uncertain; reasonable options include every five years, with a shorter interval for those with high-normal lipid levels and longer intervals for low-risk individuals with low or normal levels.

��There is no recommendation to stop screening at a particular age.

��Screening may be appropriate in older people who have never been screened, although screening a second or third time is less important in older people because lipid levels are less likely to increase after age 65.

HIGH CHOLESTEROL TREATMENTS

The treatment options for people with high cholesterol and lipids are discussed separately.