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Revision:Factors Effecting Coronary heart disease
From The Student RoomTSR Wiki > Study Help > Subjects and Revision > Revision Notes > Biology > Factors Effecting Coronary heart disease
What is Coronary Heart Disease (CHD)?CHD has two principal forms - angina and heart attacks (myocardial infraction). Both occur because the arteries carrying blood to the heart muscle become blocked or narrowed, usually by a deposit of fatty substances, a process known as atherosclerosis. Angina is a severe pain in the chest brought on by exertion and relieved by rest. A heart attack is due to obstruction of a coronary artery either as a result of atherosclerosis or a blood clot: part of the heart muscle is deprived of oxygen and dies. (Michael Roberts, Michael Reiss and Grace Mange, Advanced biology 2000; page 24)
Risk factors for Coronary Heart DiseaseCigarette smoking, raised blood cholesterol and high blood pressure are the most firmly established, non-hereditary risk factors leading to CHD with cigarette smoking being the 'most important of the known modifiable risk factors for CHD', according to the US Surgeon General. (US DHHS The health benefits of smoking cessation - a report of the Surgeon General, 1990.) A cigarette smoker has two to three times the risk of having a heart attack than a non-smoker. If both of the other main risk factors are present then the chances of having a heart attack can be increased eight times. (Doll, R and Peto, R. Mortality in relation to smoking. Br Med J. 1976.) At least 80% of heart attacks in men under 45 are thought to be due to cigarette smoking. (Townsend, JL and Meade, TW. J Epidemiol Health 1979; pages 33: 243-247) At this age, heavy smokers have 10 to 15 times the rate of fatal heart attacks of non-smokers. Even light smokers are at increased risk of CHD: a US study found that women who smoked 1-4 cigarettes a day had a 2.5-fold increased risk of fatal coronary heart disease. (Bartecchi CE, et al. New England Journal of Medicine 1994; pages 330: 907-912) Other factors include being male, age, having close relative who have had heart attacks being overweight, taking to little exercise, having high blood pressure and eating too much salt or saturated fat or too little fibre. The relation between fat intake and the risk of coronary heart disease is not fully understood, however it does seem clear though that a high level of saturated fats and cholesterol in the diet is associated with an increased risk of coronary heart disease. (Michael Roberts, Michael Reiss and Grace Mange, Advanced biology 2000; page 24)
AgeThe risk of coronary atherosclerosis increases with age, but evidence suggests that the condition may start to develop very early in life. About four out of five people who die of coronary heart disease are age 65 or older. At older ages, women who have heart attacks are more likely than men are to die from them within a few weeks. SexWomen before menopause rarely suffer from heart disease (the hormone oestrogen present in women appears to protect them.) Coronary heat disease mainly afflicts adult males and manifests itself in the middle ages (45-55 years old). DietIndividuals with hereditary high levels of blood cholesterol are more prone to develop coronary heart disease. The risk of coronary heart disease rises as blood cholesterol levels increase. When other risk factors (such as high blood pressure and tobacco smoke) are present, this risk increases even more. A person's cholesterol level is also affected by age, sex and heredity. SmokingTends to increase blood cholesterol levels. Cigarette smokers also have raised fibrinogen levels and platelet counts, which make the blood stickier. Carbon monoxide attaches itself to haemoglobin much more easily than oxygen does. This reduces the amount of oxygen available to the tissues. All these factors make smokers more at risk of developing various forms of atherosclerotic disease. As the atherosclerotic process progresses, blood flows less easily through rigid and narrowed arteries and the blood is more likely to form a thrombosis. This sudden blockage of an artery may lead to a fatal heart attack, a stroke or gangrene. High blood pressureIncreases the heart's workload, causing the heart to enlarge and weaken over time. It also increases the risk of stroke, heart attack, kidney failure and congestive heart failure. When high blood pressure exists with obesity, smoking, high blood cholesterol levels or diabetes, the risk of heart attack or stroke increases several times. WeightPeople who have excess body fat - especially if a lot of it is in the waist area - are more likely to develop heart disease and stroke even if they have no other risk factors. Excess weight increases the strain on the heart, raises blood pressure and blood cholesterol and triglyceride levels, and lowers HDL ('good') cholesterol levels. It can also make diabetes more likely to develop. HeredityCoronary heart disease is much more common in some families than in others. As DNA determines the sizes of the arteries themselves it is probable that characteristics of the heart are passed on to offspring. Lack of exerciseRegular exercise aids a healthy circulation, and the physically inactive are more at risk from heart disease. Other diseasesDiabetes and high blood pressure increase the risk of coronary disease. Diabetes seriously increases the risk of developing cardiovascular disease. Even when glucose levels are under control, diabetes greatly increases the risk of heart disease and stroke. About two-thirds of people with diabetes die of some form of heart or blood vessel disease. Socio-economic disadvantageAs nations become prosperous coronary heart disease becomes less of a problem for the well educated classes, and preferentially affects those in the lower social levels; poor housing and little education are strong indicators of high coronary mortality. Psychological and personality factorsSleep disturbances and stress are predictors of angina, infraction and death due to heart attacks. Birth control pillsHigher doses of oestrogen and progestin, increase a woman's risk of heart disease and stroke, especially in older women who smoked heavily. Newer, lower-dose oral contraceptives carry a much lower risk of cardiovascular disease, except for women who smoke or have high blood pressure. If a woman taking oral contraceptives has other risk factors (and especially if she smokes), her risk of developing blood clots and having a heart attack goes up. It rises even more after age 35.
Clustering of Risk FactorsThe tendency of risk factors to cluster in a single individual is being increasingly recognized. (Williams RR, Hunt SC, Hopkins PN, Stults BM, Wu LL, Hasstedt SJ, Barlow GK, Stephenson SH, Lalouel JM, Kuida H. Familial dyslipidemic hypertension: evidence from 58 Utah families for a syndrome present in approximately 12% of patients with essential hypertension. JAMA. 1988; 259:3579-3586.) AND (Working Group Report on Management of Patients with Hypertension and High Blood Cholesterol. Bethesda, Md: US Dept of Health and Human Services; National Heart, Lung, and Blood Institute; 1990. NIH publication No. 90-2361.) Obesity and physical inactivity contribute importantly to the development of multiple risk factors in the American population; this clustering of multiple metabolic risk factors is called the metabolic syndrome. (Grundy SM. Small LDL, atherogenic dyslipidemia, and the metabolic syndrome. Circulation. 1997; 95:1-4.) Risk will be further accentuated in smokers with several metabolic risk factors. There is an increasing need to identify persons with multiple risk factors and, because of their high risk, to initiate management directed at all risk factors. (C J Clegg with D G Maclean, Advanced Biology principles and applications 1994, page 361) AND (Fractos Affecting Conary Heart Disease) AND (www.ash.org).
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