To understand high blood cholesterol, it helps to learn about cholesterol. Cholesterol is a waxy, fat-like substance that’s found in all cells of the body.
Your body needs some cholesterol to make hormones, vitamin D, and substances that help you digest foods. Your body makes all the cholesterol it needs. However, cholesterol also is found in some of the foods you eat.
Cholesterol travels through your bloodstream in small packages called lipoproteins. These packages are made of fat (lipid) on the inside and proteins on the outside.
Two kinds of lipoproteins carry cholesterol throughout your body: low-density lipoproteins (LDL) and high-density lipoproteins (HDL). Having healthy levels of both types of lipoproteins is important.
LDL cholesterol sometimes is called “bad” cholesterol. A high LDL level leads to a buildup of cholesterol in your arteries. (Arteries are blood vessels that carry blood from your heart to your body.)
HDL cholesterol sometimes is called “good” cholesterol. This is because it carries cholesterol from other parts of your body back to your liver. Your liver removes the cholesterol from your body.
What Is High Blood Cholesterol?
High blood cholesterol is a condition in which you have too much cholesterol in your blood. By itself, the condition usually has no signs or symptoms. Thus, many people don’t know that their cholesterol levels are too high.
People who have high blood cholesterol have a greater chance of getting coronary heart disease, also called coronary artery disease. (In this article, the term “heart disease” refers to coronary heart disease.)
The higher the level of LDL cholesterol in your blood, the GREATER your chance is of getting heart disease. The higher the level of HDL cholesterol in your blood, the LOWER your chance is of getting heart disease.
Coronary heart disease is a condition in which plaque builds up inside the coronary (heart) arteries. Plaque is made up of cholesterol, fat, calcium, and other substances found in the blood. When plaque builds up in the arteries, the condition is called atherosclerosis
What are atheroma and cardiovascular diseases?
Patches of atheroma are like small fatty lumps that develop within the inside lining of blood vessels (arteries). Atheroma is also known as atherosclerosis and hardening of the arteries. Patches of atheroma are often called plaques of atheroma.
Over months or years, patches of atheroma can become larger and thicker. So in time, a patch of atheroma can make an artery narrower. This can reduce the blood flow through the artery. For example, narrowing of the heart (coronary) arteries with atheroma is the cause of angina.
Sometimes, a blood clot (thrombosis) forms over a patch of atheroma and completely blocks the blood flow. Depending on the artery affected, this can cause a heart attack, a stroke, or other serious problems.
Cardiovascular diseases are diseases of the heart (cardiac muscle) or blood vessels (vasculature). However, in practice, when doctors use the term cardiovascular disease they usually mean diseases of the heart or blood vessels that are caused by atheroma.
In summary, cardiovascular diseases caused by atheroma include angina, heart attack, stroke, transient ischaemic attack (TIA) and peripheral arterial disease.
What factors affect the blood level of cholesterol?
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 underactive thyroid gland, obesity, drinking a lot of alcohol and some rare kidney and liver disorders can raise the cholesterol level.
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 your body. One example is called familial hypercholesterolaemia.
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:
o Lack of physical activity (a sedentary lifestyle).
o An unhealthy diet - including eating too much salt.
o Excess alcohol.
• Treatable or partly treatable risk factors:
o High blood pressure (hypertension).
o High cholesterol blood level. However, only LDL cholesterol is a risk factor. HDL cholesterol is healthy for your body.
o High triglyceride (another type of fat) blood level.
o Kidney diseases that affect kidney function.
Fixed risk factors - ones that you cannot alter
• A strong family history. 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.
• Being male.
• 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 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.
Note: 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 blood levels
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:
• 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 after an overnight fast: 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.
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.
Calculating your cardiovascular health risk
A risk factor calculator is commonly used by doctors and nurses. This can assess your cardiovascular health risk. A score is calculated which takes into account all your risk factors such as age, sex, smoking status, blood pressure, cholesterol level, etc.
The calculator has been devised after a lot of research that monitored thousands of people over a number of years. The score gives a fairly accurate indication of your risk of developing a cardiovascular disease over the following 10 years. If you want to know your score, see your practice nurse or GP.
Who should have their cardiovascular health risk assessed?
It is advised that the following people should be assessed to find their cardiovascular health risk:
• All adults aged 40 or more.
• Adults of any age who have:
o A strong family history of early cardiovascular disease. 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.
o A first-degree relative (parent, brother, sister, child) with a serious hereditary lipid disorder. For example, familial hypercholesterolaemia or familial combined hyperlipidaemia. These diseases are uncommon.
If you already have a cardiovascular disease or diabetes then your risk does not need to be assessed. This is because you are already known to be in the high-risk group.
What does the assessment involve?
A doctor or nurse will:
• Do a blood test to check your cholesterol and sugar (glucose) level.
• Measure your blood pressure and your weight.
• Ask you if you smoke.
• Ask if there is a history of cardiovascular diseases in your blood relations. If so, at what age the diseases started in the affected family members.
A score is calculated based on these factors plus your age and your sex. An adjustment to the score is made for certain other factors, such as strong family history and ethnic origin.
What does the assessment score mean?
You are given a score as a percentage chance. So, for example, if your score is 30% this means that you have a 30% chance of developing a cardiovascular disease within the following 10 years. This is the same as saying a 30 in 100 chance (or a 3 in 10 chance). In other words, in this example, 3 in 10 people with the same score that you have will develop a cardiovascular disease within the following 10 years.
The score tells you have a:
• High risk - if your score is 20% or more. That is a 2 in 10 chance or more of developing a cardiovascular disease within the following 10 years.
• Moderate risk - if your score is 10-20%. That is between a 1 in 10 and 2 in 10 chance.
• Low risk - if your score is less than 10%. That is less than a 1 in 10 chance.
Who should be treated to reduce their cardiovascular health risk?
Treatment to reduce the risk of developing a cardiovascular disease is usually offered to people with a moderate or high risk. That is:
• People with a risk assessment score of 10-20% or more. That is, if you have a 1 or 2 in 10 chance or more of developing a cardiovascular disease within the following 10 years.
• People with an existing cardiovascular disease (to lower the chance of it getting worse, or of developing a further disease).
• People with diabetes. If you have diabetes, the time that treatment is started to reduce cardiovascular risk depends on factors such as:
o Your age.
o How long you have had diabetes.
o Your blood pressure.
o If you have any complications of diabetes.
• People with certain kidney disorders.
The following people should also have medication to lower their cholesterol level, regardless of any calculated risk. The risk calculator may not necessarily take into account these people, who have a high risk of developing small fatty lumps (atheroma) that develop within the inside lining of blood vessels (arteries):
• People with a TChol to HDL ratio of 6 or more (TChol/HDL = 6 or more).
• People with inherited lipid disorders.
What treatments are available to reduce the risk?
Everyone should aim to tackle lifestyle risk factors. This means to:
• Stop smoking if you smoke.
• Eat a healthy diet.
• Keep your salt intake to under 6 g a day.
• Keep your weight and waist in check.
• Take regular physical activity.
• Cut back if you drink a lot of alcohol.
If available (and if required) you may be offered a referral to a specialist service. For example, to a dietician to help you to lose weight and eat a healthy diet, to a specialist stop smoking clinic, or to a supervised exercise programme.
If you are at moderate or high risk of developing a cardiovascular disease then treatment with medication is usually advised along with advice to tackle any lifestyle issues. This usually means:
• A medicine to lower your cholesterol level, usually with a statin medicine. No matter what your current cholesterol level, treatment is advised. There are several different statin medicines. They work by blocking a chemical (enzyme) which is needed to make cholesterol in the liver.
There is no actual target level for people who do not already have cardiovascular disease. However, for those who do have a cardiovascular disease, the aim, if possible, is to reduce TChol to less than 4.0 mmol/L and LDL cholesterol to less than 2.0 mmol/L.
• Treatment to lower blood pressure if it is high. This is even if your blood pressure is just mildly high.
In addition, if you already have cardiovascular disease, a daily low dose of a medicine called an antiplatelet medicine (aspirin is one example) is also usually advised. This helps to prevent blood clots from forming on patches of atheroma.
What happens when I take a statin?
You should have a blood test before starting treatment. This checks the level of cholesterol. It also checks if your liver is working properly. After starting treatment you should have a blood test within 1-3 months, and again at 12 months. The blood test is to check that the liver has not been affected by the medication. The blood may also be checked to measure the cholesterol level to see how well the statin is working.
What is the target cholesterol level to aim for?
There is no actual target cholesterol blood level for people who do not already have cardiovascular disease.
If you do have a cardiovascular disease the aim, if possible, is to reduce total cholesterol (TChol) to less than 4.0 mmol/L and low-density lipoprotein (LDL) cholesterol to less than 2.0 mmol/L. If the target is not reached at first, the dose may need to be increased or a different preparation used.
What are the possible side-effects or problems with statins?
Most people who take a statin have no side-effects, or only minor ones. Read the information leaflet that comes with your medicine. It will have a full list of possible side-effects. They include headache, pins and needles, tummy (abdominal) pain, bloating, diarrhoea, feeling sick (nausea), and a rash.
Some people are prescribed very high doses of statins. This is usually because they have a high risk of cardiovascular disease or lower doses have not worked. Some recent research has shown this may increase their risk of developing diabetes. This happens about once for every 500 people treated this way. This needs to be balanced against the benefits. For about every 155 people treated with very high doses of statins, there is one less heart attack or stroke.