Links Between Smoking and Disease
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Links Between Smoking and Disease
These can be put into two groups:
Epidemiological evidence looks for patterns in the diseases, which smokers suffer from. It only shows an association and not a causal link.
Experimental evidence attempts to prove a causal link.
Chronic obstructive pulmonary disease is very rare in non-smokers and 90% of deaths from it can be attributed to smoking. 98% of people with emphysema smoke and 20% of smokers suffer from it. Deaths from pneumonia and influenza are twice as high among smokers.
Lung cancer is eighteen times more likely in smokers and one third of all cancer deaths can be attributed to smoking. 25% of smokers die from lung cancer and the risks are higher if they inhale, start young, smoke a large number of cigarettes a day and smoke over a long period of time.
The risks of developing lung cancer fall as soon as smoking stops but it takes ten years for the risks to fall to that of a non-smoker.
Experimental evidence includes the development of tumours in animals exposed to smoke and the identification of carcinogens in tar. Both lung cancer and chronic obstructive lung disease have been observed in dogs and tar has caused cancerous growths in the skin of mice.
Cardiovascular diseases are degenerative diseases of the heart and circulatory system. They are responsible for 50% of deaths in developed countries and are multifactorial - smoking being one risk factor.
This is caused by a build-up of fatty material in artery walls, which reduces the flow of blood and therefore oxygen to the tissues. An atheroma is a build up of cholesterol, fibres, dead muscle cells and platelets and is more likely to develop upon damage to the artery wall by high blood pressure, carbon monoxide or nicotine.
Blood clots (thrombosis) become more likely and if one develops in the coronary artery a heart attack may be the result, while if it occurs in an artery supplying the brain, a stroke may result.
Three forms exist:
Angina is severe chest pains upon exercising caused by a shortage of blood to the heart muscle but causes no death of heart tissue and stops upon resting.
Heart attacks occur upon the blocking of a moderate branch of the coronary artery by a blood clot and cause starvation and death of heart tissue.
Heart failure is when the coronary artery starts to block up and results in a gradual weakening of the heart.
These occur if an artery in the brain bursts and blood leaks into the brain tissue or when an artery supplying the brain becomes blocked. The brain tissue becomes starved of oxygen and dies. Strokes can be fatal or very mild and may affect speech, memory and control of the body.
Smoking increases the concentration of blood cholesterol, which is a risk factor, so smokers increase the risk of having heart disease or a stroke. The risks of developing the disease increases with age and men are more at risk than women.
Being overweight increases the risk as does eating a diet high in saturated fat and salt. Diets with more antioxidants (vitamins) and soluble fibre decrease the risk as does taking regular exercise. Having diabetes raises the risks and high alcohol intake is another contributory factor.
This is a disease associated with affluence and is avoidable by a change in lifestyle.
Drugs to lower blood pressure, decrease risks of clots, reduce retention of fluids and decrease blood cholesterol.
Coronary by-pass surgery involves the use of blood vessels from - for example, a leg to replace a diseased vessel and carry blood from the aorta to a place beyond the blockage.
Heart transplants are very expensive and it is difficult to obtain matching tissue from donors.
Better than treatment is obviously prevention. This can be achieved via education highlighting the risk factors and by screening for those most at risk. Unfortunately, bad eating and smoking are hard habits to kick.