Raised levels of cholesterol in the blood, which increase the risk of developing cardiovascular disease
- More common with increasing age
- More common in males
- Sometimes runs in families
- A diet high in saturated fats, obesity, and lack of exercise are risk factors
An estimated 2 in 3 adults in the UK have a high blood cholesterol level (above 5 mmol/L). Raised cholesterol levels are associated with increased risk of coronary artery disease and stroke due to atherosclerosis.
Cholesterol is a substance known as a lipid. It is used in the manufacture of cell walls and in the production of bile acids (which aid the digestion of fat) and important steroid hormones. The liver produces most of the body’s cholesterol, but some cholesterol is derived from food, such as eggs, meat, and shellfish. Diet (see Diet and health) and other lifestyle factors can affect the cholesterol level.
Cholesterol is carried in the blood in the form of lipid–protein particles known as lipoproteins. There are two main types: low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs). LDLs carry larger amounts of cholesterol than HDLs and deposit it around the body. Raised levels of LDLs increase the risk of arterial disease. The excess LDLs form fatty deposits on the walls of arteries (atherosclerosis). As these deposits grow, they restrict blood flow and cause the formation of clots that block the vessels. HDLs pick up cholesterol molecules from the tissues and fatty deposits of atherosclerosis and return them to the liver to be broken down. A high level of HDLs thus protects against arterial disease.
What are the causes?
Cholesterol level is determined by a combination of genetic and lifestyle factors. A high level is associated with a diet that is high in fats, particularly saturated fats, being overweight, and lack of exercise. Although the condition often runs in families, some people have specific inherited hyperlipidaemias, which are associated with extremely high cholesterol levels.
A high cholesterol level does not usually cause symptoms until it leads to the development of another disorder, such as coronary artery disease.
How is it diagnosed?
Regular screening tests to measure the blood cholesterol level are recommended from early adult life for people with a family history of raised cholesterol levels, heart disease, or stroke. The tests may also be offered after the age of 40 as part of a general health checkup. Hypercholesterolaemia is frequently first diagnosed as a result of a routine screening test.
The optimal total cholesterol level for a middle-aged person is less than 5 mmol/L. If the total cholesterol level exceeds 5 mmol/L, your doctor may carry out a further blood test to check your levels of LDL and HDL cholesterol.
What is the treatment?
Whether or not you require treatment depends on how high your blood cholesterol level is and whether other risk factors for coronary artery disease, such as high blood pressure (see Hypertension) or smoking, are present. Even if your cholesterol level falls within the normal range, you may be given treatment to lower cholesterol if you have heart disease or risk factors for atherosclerosis.
If you are found to have an excessively high cholesterol level, your doctor may initially advise you about changes in diet and exercise habits that should lower it. However, if these measures fail to lower the level sufficiently, your doctor may prescribe drugs, which you are likely to need to take for the rest of your life (see Lipid-lowering drugs).
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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