Hypercholestérolémie

What is high cholesterol?

High cholesterol refers to elevated levels of cholesterol in the blood. If your cholesterol levels are high, this can increase the chance of build-up of fatty deposits in your arteries. This increases the risk of heart attack and stroke.

Cholesterol is carried in the blood by particles called lipoproteins. When low-density lipoproteins (LDL cholesterol) carry cholesterol this is referred to as 'bad' cholesterol. Higher levels of LDL cholesterol in your blood cause an increased risk of lipoprotein disorders and cardiovascular disease (heart and blood vessel diseases, such as heart attack and stroke).

However, some cholesterol in your blood is carried by high-density lipoproteins (HDL cholesterol). HDL cholesterol can be thought of as 'good' cholesterol and higher levels help to prevent cardiovascular disease.

Other factors that can reduce your risk of cardiovascular disease include not smoking, choosing healthy foods, a low salt intake, regular physical activity, keeping your weight and waist size down and drinking alcohol in moderation (if at all). Ensuring your blood pressure level is not raised (or taking medication to lower it if it is high) is also important.

Voir la brochure séparée intitulée Maladie cardiovasculaire (Athérome).

Most people with high cholesterol have no symptoms. Very occasionally, some people have fatty, cholesterol-rich deposits which are visible under their skin. These are called xanthelasma or xanthoma. Another rare visible sign is an arcus senilis - a white ring around the cornea (the coloured part of the eye).

Everybody has some risk of developing small fatty lumps (atheroma) within the inside lining of blood vessels, which then may cause one or more cardiovascular diseases. However, some situations increase the risk. These include:

• Lifestyle risk factors that can be prevented or changed:
  

  • Tabagisme.

  • Lack of physical activity (a sedentary lifestyle).

  • Obésité.

  • An unhealthy diet - including eating too much salt.

  • Excess alcohol.

• Treatable or partly treatable risk factors:
  

  • Hypertension artérielle (hypertension).

  • High cholesterol level. However, only LDL cholesterol is a risk factor. HDL cholesterol is healthy for your body.

  • High triglyceride (another type of fat in your blood) level .

  • Diabète.

  • Kidney diseases that affect kidney function.

Fixed risk factors - ones that you cannot change

• A strong family history of high cholesterol. This means if you have a father or brother who developed heart disease or a stroke before they were 55, or in a mother or sister before they were 65.

• Être de sexe masculin.

• An early menopause in women.

• Age. You are more likely to develop atheroma as you get older.

• Ethnic group. For example, people who live in the UK whose family originally came from India, Pakistan, Bangladesh or Sri Lanka have an increased risk.

However, if you have a fixed risk factor, you may want to make extra effort to tackle any lifestyle risk factors that can be changed. Voir la brochure séparée intitulée Maladie cardiovasculaire (Athérome).

Remarque: risk factors interact. So, if you have two or more risk factors, your health risk is much more increased than if you just have one. For example, a middle-aged male smoker who has high blood pressure and a high cholesterol level has a high risk of developing a cardiovascular disease, such as a heart attack, before the age of 60.

Cholesterol levels are tested with a simple blood test. This can be done in two ways. The blood can be taken from your arm with a needle and sent to a lab for analysis. The result will come back in a few days. In some places it is possible to have your cholesterol tested with a finger prick test. This gives the result in a few minutes. It is not usually necessary to fast before cholesterol tests.

Cholesterol blood levels are very important but must be considered in an overall assessment of your risk of cardiovascular disease (see below). The following blood cholesterol levels are generally regarded as desirable for people who are otherwise at low risk:

• Total cholesterol (TChol): 5.0 mmol/L or less. However, about 2 in 3 adults in the UK have a TChol level of 5.0 mmol/L or above.

• LDL cholesterol: 3.0 mmol/L or less.

• HDL cholesterol: 1.2 mmol/L or more.

• TChol/HDL ratio: 4.5 or less. That is, your TChol divided by your HDL cholesterol. This reflects the fact that for any given TChol level, the more HDL, the better.

If other factors mean you are at a higher risk for cardiovascular disease - eg, you have had a stroke - it is recommended that your target levels for LDL cholesterol should be lower.

As a rule, the higher the LDL cholesterol level, the greater the risk to health. A blood test only measuring total cholesterol may be misleading. A high total cholesterol may be caused by a high HDL cholesterol level and is therefore healthy. It is very important to know the separate LDL cholesterol and HDL cholesterol levels.

Your level of LDL cholesterol has to be viewed as part of your overall cardiovascular health risk. The cardiovascular health risk from any given level of LDL cholesterol can vary, depending on the level of your HDL cholesterol and on any other health risk factors that you may have. Therefore, a cardiovascular risk assessment considers all your risk factors together.

To an extent your blood cholesterol level can vary depending on your diet. However, different people who eat the same diet can have different blood cholesterol levels. In general, however, if you eat less fatty food in your diet your cholesterol level is likely to go down.

In some people a high cholesterol level is due to another condition. For example, an glande thyroïde sous-active, obesity, drinking a lot of alcohol and some rare kidney and liver disorders can raise the cholesterol level. Hyperlipidaemia means too much lipid (particularly cholesterol) in your bloodstream. See the separate leaflet called Hyperlipidaemia.

In some people a very high level of cholesterol runs in the family, due to a genetic problem with the way cholesterol is made by the cells in the body. One example is called familial hypercholesterolaemia. See the separate leaflet called Familial hypercholesterolaemia.

If you have a high risk of developing a cardiovascular disease, or you already have a cardiovascular disease, lowering your LDL cholesterol level reduces your risk of developing future cardiovascular problems.

For details on exactly how much risk is reduced by lowering and treating risk factors, find out more about the National Institute for Health and Care Excellence Clinical Knowledge Summary (NICE CKS), 'Cardiovascular risk assessment and management' (note UK access only).

Changing your diet

Changing from an unhealthy diet to a healthy diet can reduce your LDL cholesterol level. It is advisable to reduce the saturated fat and trans fat in your diet. However, dietary changes alone rarely lower an LDL cholesterol level enough to change a person's risk of cardiovascular disease from a high-risk category to a lower-risk category.

Statines

A medicine (usually a medicine called a statin) is often used if you are at increased risk of cardiovascular disease. Read about cholesterol-lowering treatments in the separate leaflet called Hyperlipidaemia.

Even if you have a low risk of cardiovascular disease it is still very important to follow the healthy lifestyle advice. This advice, including healthy eating, regular exercise, not smoking and drinking alcohol only in moderation (if at all), will help to keep your risk of cardiovascular disease as low as possible.