What is Cholesterol?
Cholesterol is a soft, wax-like substance which is found in the walls or membranes of every cell in our body. It is also a key component in the manufacture of hormones (chemical messengers in our body) and bile acids which work in our intestines to help promote the absorption of fat from our diets.
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 cardiovascular disease. 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.
What factors affect the blood level of cholesterol?
Blood cholesterol level can, to some extent, 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 hypercholesterolemia.
Every person 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:
- Lack of exercise
- Unhealthy diet
- Excess alcohol
Treatable or partly treatable risk factors:
- High blood pressure (hypertension).
- High cholesterol blood level – only LDL cholesterol is a risk factor. HDL cholesterol is healthy for your body.
- High triglyceride (another type of fat) blood level.
- Kidney diseases that affect kidney function.
Fixed risk factors – ones that you cannot alter:
- A strong family history.
- Being male
- Early menopause in women.
- Age. You are more likely to develop atheroma as you get older
- Ethnic group.
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.
It is important to note that 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.
Cholesterol blood levels
Cholesterol blood levels are very important but must be considered in an overall assessment of your risk of cardiovascular disease. The following blood cholesterol levels are generally regarded as desirable:
- Total cholesterol (TChol) – 5.0 mmol/L or less.
- 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.
Who should have their cardiovascular health risk assessed?
Current guidelines advise 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:
- 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.
- A first-degree relative (parent, brother, sister, child) with a serious hereditary lipid disorder.
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 an assessment involve?
Our clinicians 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.
Note: the score cannot say if you will be one of the three. It cannot predict what will happen to each individual person. It just gives you the odds.
You are said to 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.
Treatment to reduce the risk of developing a cardiovascular disease is usually offered to people with a moderate or high risk.
Treatment is also normally recommended for:
- people with an existing cardiovascular disease (to lower the chance of it getting worse, or of developing a further disease).
- People with diabetes.
- People with certain kidney disorders.
People with a TChol to HDL ratio of 6 or more (TChol/HDL = 6 or more) and people with inherited lipid disorders should also review their cholesterol with their Doctor.
What treatments are available?
Everyone should aim to tackle lifestyle risk factors:
- Stop smoking if you smoke.
- Eat a healthy diet.
- Keep your salt intake to under 6g per day.
- Manage your weight responsibly.
- Exercise regularly.
- Reduce alcohol intake.
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.
If you would like to discuss any issues relating to your cholesterol or health generally then please make an appointment to see one of our Doctors at www.cssdoctor.ie. We are here to help you!
Extracts from patient.info/health/cholesterol