Factors affecting the Development of Coronary Heart Disease
Factors affecting the Development of Coronary Heart Disease
The aim of this essay is to identify the factors affecting the development of coronary heart disease (CHD).
CHD refers to atherosclerosis of the coronary arteries. Atherosclerosis is the result of an atheroma forming in an artery or the hardening of the arteries, which is the build up of fat deposits forming on the walls of the artery (see figure one). Atheroma causes a reduction in blood-flow in one or more of the arteries and blood clots are more likely to form as the lumen progressively becomes narrower. Heart cells are dependent on blood flow to provide oxygen and nutrients for the heart muscle to be able to function properly. Without the right conditions and coronary arteries becoming blocked, a myocardial infarction can occur (heart attack).
Figure 1 - The development of an atheroma forming (1)
The factors effecting CHD are classified into non-modifiable and modifiable factors. The table below shows that the more risks a person has, the higher the chance of developing CHD.
Figure 2 (2)
The non-modifiable factors are genetic factors, gender, age and diabetes mellitus.
Genetic factors have proven to have an influence on the risk of CHD. "People with parents who suffered CHD are more likely to develop it themselves" (3). A reason why CHD runs in families is that parents may pass on genes to their children that render them more liable to have high cholesterol, develop high blood pressure or have diabetes mellitus.
There is a trend in the age and gender risk factors. It is more common for men under the age of fifty-five to develop CHD than women. Women's risk of CHD increases after the menopause, the reasons have not been scientifically proven, "The exact reason why women are protected from CHD before the menopause is not known for sure, but it does seem likely that this is related to hormones that disappear once menstruation stops" (4). Hormone replacement therapy (HRT) seems to help in reducing this risk factor. This is a reason why doctors recommend HRT. For both ...
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There is a trend in the age and gender risk factors. It is more common for men under the age of fifty-five to develop CHD than women. Women's risk of CHD increases after the menopause, the reasons have not been scientifically proven, "The exact reason why women are protected from CHD before the menopause is not known for sure, but it does seem likely that this is related to hormones that disappear once menstruation stops" (4). Hormone replacement therapy (HRT) seems to help in reducing this risk factor. This is a reason why doctors recommend HRT. For both genders, the risk of CHD is roughly even at the age of seventy-five and above.
Diabetes sufferers have a high risk of developing CHD because they have high blood cholesterol, "Elevated blood lipid levels (cholesterol and triglycerides) also increase the risk of coronary artery disease. Since high blood lipid levels are common in people with diabetes, many diabetic patients are on lipid-lowering medication"(5).
Modifiable factors of risk are smoking, raised cholesterol levels from the diet, physical inactivity, high blood pressure and stress.
Smoking is strongly related to the high risk of CHD. The chemicals in cigarette smoke, mainly carbon monoxide, enter into the lungs and are absorbed into the blood stream; carbon monoxide reduces the red blood cells ability to carry oxygen to the body cells in haemoglobin. These chemicals cause blood platelets to become stickier, which increase the chance of blot clots forming (see figure three). Nicotine in cigarettes causes vasoconstriction, which in turn increases blood pressure. Pipe and cigar smokers are not at such a high risk as cigarette smokers, however, they are more at risk than a non-smoker. Quitting smoking helps in reducing the risk of CHD, but the risk will never be as low as a non-smoker.
Figure 3 - Chemicals in smoking causing blood platelets to become stickier. (6)
A cholesterol-rich diet increases the risk of an atheroma (as mentioned above) forming. This is because cholesterol is a type of lipid (fat) that combines with proteins in the blood to form lipoproteins. There are two types of lipoprotein, low-density lipoproteins (LDL) that increase the risk of developing atheromas and high-density lipoproteins (HDL), which do not contribute to atheromas but they can make LDL cholesterol less dangerous to health. Eating a cholesterol-rich diet, especially animal and dairy fats, will increase the amount of LDL in the blood. Physical activity will increase the amount of HDL, which helps to reduce the dangers of LDL. Regular exercise also helps to prevent high blood pressure and obesity, which both contribute to the development of CHD.
Obese people carry a very large amount of excess body fat, this increases the risk of CHD, as atheroma is more likely to form in the coronary arteries from cholesterol, which will result in atherosclerosis, also the strain of excess body weight can cause high blood pressure.
High blood pressure is where the heart has to 'work harder' to pump the blood around the body by "an increase in cardiac output and by contraction of the muscle in the middle layer of the arteries" (7). Hypertension occurs when blood pressure becomes constantly at a high level and "It frequently has no symptoms until its advanced stages" (8), which causes an increased risk of CHD. This is because arteries respond to high blood pressure by making their muscular layers become thicker, narrowing the lumen, and increasing blood pressure by a further extent. While blood pressure continues to increase, the endothelium of the artery may become damaged, increasing the risk of an atheroma forming. The causes leading to hypertension are "stress, obesity, excessive consumption of alcohol, a high intake of sodium chloride and smoking tobacco" (9).
Stress is an important factor of risk for CHD, although various people have questioned it, "it has been surprisingly difficult to prove this link scientifically...attempts to make major changes in behaviour are probably of little benefit" (10). BUPA Healthcare suggests, "Stress is difficult to assess, but anything that makes excessive demands on you - especially work - seems to be associated with high blood pressure" (11). Acute stress stimulates the production of the hormone adrenaline. This makes the body release extra sugar and fats into the blood stream and makes the blood 'stickier'. This helps to prove that constant stress would increase the chance of an atheroma forming and also blood clotting.
In conclusion to the factors mentioned above, there are many actions to take into account to lower the risk of CHD occurring. The main threat is atherosclerosis, to reduce the risk of an atheroma forming in the coronary arteries people should not smoke, exercise regularly, eat a low cholesterol diet, avoid excessive consumption or binge drinking of alcohol, lower the intake of sodium chloride and 'tone down' any hectic form of lifestyle to avoid stress. The more risks that a person has in their life; the more chance they have of developing CHD.
