Heart disease: the risk factors

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Almost all cases of coronary heart disease (CHD) are due to atherosclerosis (blockage of the arteries, especially of the coronary arteries which supply the heart muscle). A variety of factors, often acting together, are associated with an increased risk of atherosclerosis, and thus of CHD.

Some of these factors are beyond our control – such as age and gender – but others can be modified to greatly lower risk. Such factors include medical conditions (e.g. hypertension) and lifestyle factors (e.g. diet and exercise).

Known risk factors for CHD include:

1. Family history
This is an important risk factor for CHD, particularly if one parent has had documented, premature CHD, i.e. a father who had CHD before age 55 or a mother who had CHD before age 65. Family history nearly doubles the risk of developing CHD, and it's a risk factor that can't be modified.

2. Gender and age
Men are at a slightly increased risk of developing CHD, as are older persons. But women and younger people are by no means unaffected. In fact, heart disease is an important killer of women worldwide. Gender and age are, of course, also risk factors that cannot be changed.

3. Blood lipids
Total blood cholesterol level is an established risk factor for CHD, and the risk increases progressively the higher the level.

Of importance is not only the total, but also the levels of LDL (bad), HDL (good) cholesterol and triglycerides (a type of fat found in the blood). The ideal cholesterol levels for a person with no known CHD risk factors are

• Normal total cholesterol: <4 mmol/l
• Normal triglycerides: <2 mmol/l
• Low LDL: <2 mmol/l
• High HDL: >1 mmol/l

If these levels are abnormal, there is a higher risk that can atherosclerosis will develop i.e. cholesterol plaques are deposited in the coronary arteries, which can lead to angina and heart attack. Blood clots tend to form at these plaques, and this can cause further, or even total, obstruction of the artery. If a piece of this clot breaks off and is carried via the circulation to arteries in the brain, it can cause a stroke.

Normalising your cholesterol and blood lipid (fat) level can significantly delay the onset and complications of CHD.

4. Hypertension
Hypertension (high blood pressure) is called “the silent killer” because, by itself, it seldom causes any symptoms. In the long term though, persistently raised pressure in arteries increases the workload of the heart, and can accelerate the process of atherosclerosis.

Strict control of blood pressure – the ideal is not above 120/80 – drastically reduces the risk of heart disease and stroke.

5. Smoking
This is an important, reversible risk factor. Risk of heart attack is increased six times in women, and three times in men, who smoke 20 cigarettes per day, compared to those who have never smoked.

The risk is immediately reduced when a person stops smoking. Smoking cessation also has an instant, positive effect on the lungs.

6. Diabetes
Statistically, having diabetes carries the same risk of heart disease as that for a person who has already had a full-blown heart attack.

In addition, diabetics have a greater burden of other atherosclerosis-inducing risk factors, such as hypertension, obesity, raised cholesterol and triglyceride levels, and increased risk of clotting.

7. Obesity and related factors
Obesity aggravates all other risk factors which may already be present, and physical inactivity further increases the risk.

People who have the combination of abdominal obesity, hypertension, diabetes and high cholesterol may be labelled as having “metabolic syndrome”. This brings a marked increase in risk of CHD.

8. Other factors
• Chronic kidney disease, and even moderate impairment, increases risk of CHD.

• Post-menopausal women have increased risk of CHD, but there isn't enough evidence to advocate oestrogen replacement purely as a measure to prevent CHD.

• Depression and stress have been linked to CHD, but are difficult to measure. It is suggested that these problems act by increasing other known risk factors such as hypertension and excess alcohol consumption.

Other possible risk factors for CHD
There are a number of conditions which are statistically linked to the incidence of CHD. However, it hasn't been proved that they are causative factors. These include:

• High resting pulse rate.

• High blood homocysteine levels (homocysteine is a component of protein). However, research shows that lowering these levels doesn’t protect against CHD.

• Hyperuricaemia (gout).

• Acute or chronic infection.

• Collagen diseases such as systemic lupus erythematosus (SLE) or rheumatoid arthritis.

• Air pollution. Fine particles such as those in diesel fumes have been implicated as potential triggers for CHD.

• Antioxidants. However, use of antioxidant supplements has shown no clear benefit in reducing CH.
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