Smoking and cardiovascular disease
Cardiovascular disease (CVD) is an umbrella term describing a variety of disease processes related to the functioning of the heart and the circulatory system. Whenever a person smokes a cigarette, the chemicals in cigarette smoke, particularly nicotine and carbon monoxide, damage the cardiovascular system. Nicotine causes both immediate and longer term increases in blood pressure, heart rate, cardiac output and coronary blood flow. Carbon monoxide binds to the haemoglobin, which is what normally carries oxygen from the lungs via the bloodstream, and therefore reduces the amount of oxygen reaching body tissues. Smoking also makes blood vessels and blood cells sticky, allowing cholesterol and other dangerous fatty material to build up inside them. This is called atherosclerosis. This in turn can lead to raised blood pressure and clot formation.
There are a number of cardiovascular diseases that can be related to smoking. They include heart disease
Cigarette smoking contributes to cardiovascular disease in a number of ways. Smoking aggravates and accelerates of the development of atherosclerotic lesions (collections of cholesterol and other matter) in the arterial walls. These collections narrow the arteries, gradually impairing blood flow, and making the arteries harder and less elastic, and more liable to rupture. The exact mechanism by which smoking exacerbates this process is not yet certain, but it is thought that the nicotine and carbon monoxide in cigarette smoke contribute to the process.
Smoking also increases heart rate and blood pressure, which raises the body's demand for oxygen, but at the same time deprives the body of oxygen through the effects of carbon monoxide. This makes the heart work even harder to meet the body's needs, which in time can lead to ischaemia (lack of oxygen due to poor blood supply), with resultant angina pectoris (chest pain or tightness) or myocardial dysfunction (poor heart muscle function).
Coronary heart disease (CHD): Coronary heart disease (mainly heart attack) is the largest single cause of death for men and women, causing more than one death every 20 minutes or 24.1% of all deaths. Smoking is one of the major risk factors for heart attack. The risk of developing CHD increases with length and intensity of exposure to cigarette smoke. Overall, smokers have a 70% greater rate of mortality from CHD than non-smokers. Smokers consuming more than 40 cigarettes per day have mortality rates between two and three times greater than non-smokers. Among people less than 65 years of age, 45% of CHD in men and 40% in women is caused by cigarette smoking.
Around half of all deaths from CHD happen without warning. Smokers are three times more likely to die suddenly because of CHD than non-smokers. In some cases, this sudden death is caused by ventricular fibrillation, which prevents the heart from beating effectively. Blockages in the arteries around the heart cause the onset of coronary heart disease (CHD). The resulting fall in oxygen supply may bring about a heart attack, due to myocardial infarction (the death of vital heart muscle), or angina (chest pain) resulting from heart muscle being starved of its blood supply and oxygen. Dysrhythmias (abnormal heart rhythms) can also occur due to lack of oxygen, or because of scarring from previous damage to the heart muscle close to the heart's electrical conducting system. Sometimes these abnormal rhythms can cause sudden death. The term 'ischaemic heart disease' (heart disease brought about by lack of oxygen) is sometimes used to describe these disease processes.
The risk of developing CHD increases with the length and intensity of exposure to cigarette smoke. Overall, smokers have a 70% greater rate of mortality from CHD than non-smokers. Smokers consuming more than 40 cigarettes per day have mortality rates between two and three times greater than non-smokers. Among people less than 65 years of age, 45% of CHD in men and 40% in women is caused by cigarette smoking. Among people 65 years of age or older, 15% of CHD in men and 9% in women is caused by smoking. In women who smoke and use the contraceptive pill there is a synergistic action, resulting in a substantial increase in risk of myocardial infarction.
Sudden cardiac death: Sudden cardiac death describes death due to major coronary artery blockage or a dangerous heart rhythm causing the heart to stop beating. It usually occurs in a patient with no previous history of heart trouble: the first sign of a problem is the unexpected death. Smokers have a two to fourfold greater risk of suffering sudden cardiac death than non-smokers. Again, the risk level increases with increased exposure to cigarette smoke.
Stroke (cerebrovascular accident): Cigarette smoking is a cause of stroke (damage to the brain due either to interruption of blood flow or the escape of blood into brain tissue from a damaged artery). This may occur because of arterial blockage due to atherosclerosis or a blood clot, or through leakage or rupture of an arterial wall at a point weakened by atherosclerosis. Frequently, the artery stretches at the site of weakness causing it to balloon out (an aneurysm). The bigger the aneurysm, the more likely it is to rupture, causing haemorrhage (bleeding) and a resultant stroke. A stroke may result in rapid death, or in varying degrees of disability, depending on the part of the brain which has been affected.
Strokes occur because of damage to the brain due to one of two things -either the blood supply to the brain is interrupted or blood has escaped into the brain. This can happen because of atherosclerosis (thickening of the arteries) or high blood pressure. Smoking may cause an artery in the brain to become blocked by a blood clot or other debris carried in the bloodstream. This cuts off the blood supply to the surrounding brain cells and causes them to die. This can affect thinking, movement, speech and/or the senses. About a third of those who have a stroke die within 12 months, with another third becoming permanently disabled. About 40,000 Australians have a stroke each year. Smokers have at least double the risk of having a stroke as a person who has never smoked, and the longer a person has smoked, and the more cigarettes per day they smoke, the greater their risk of stroke. While strokes are more common in older people, people in their 20s and 30s die from strokes too. The influence of smoking is most apparent in younger age groups. Among people less than 65 years old, it is estimated that 44% of strokes in men and 39% in women are caused by cigarette smoking.
The influence of smoking on stroke is most evident before the age of 64. Among people less than 65 years old, 44% of strokes in men and 39% in women are caused by cigarette smoking. Among people 65 years of age or older, 16% of strokes in men and 9% in women are caused by smoking. Female smokers have an increased risk for subarachnoid haemorrhage, which is due to a sudden rupture of an artery on the surface of the brain. This risk is greatly elevated among those who in addition to smoking, use the contraceptive pill.
Atherosclerotic peripheral vascular disease: Atherosclerotic peripheral vascular disease (PVD) occurs when blockages within the blood vessels prevent proper blood circulation. PVD most commonly occurs in the legs and feet, but it can also develop in the arms and hands. This may result in severe pain (claudication), especially when exercising. PVD can lead to death of part of the limb. Amputation may be necessary for relief of pain, and to prevent development of gangrene.
Smoking strongly contributes to the development of PVD, and cessation is probably the single most important intervention in its management. Ninety percent of those with atherosclerotic peripheral vascular disease are smokers. This type of cardiovascular disease occurs mainly in older people. It is a narrowing of the arteries in the extremities caused by atherosclerosis (blocked arteries) which reduces blood circulation. Mostly, this occurs in the legs and feet, but can also occur in the arms and hands. The main outcome of peripheral vascular disease is pain while walking and resting. Sometimes the blood supply is so reduced that amputation is necessary to prevent gangrene developing. Nine out of ten people with this disease are smokers. Immediately stopping smoking is the most important treatment for this disease.
Aortic aneurysm: Abdominal aortic aneurysm is a weakening of the wall of the aorta (the major artery carrying oxygenated blood from the heart to the body). The weakening occurs as a result of atherosclerotic lesions developing in the aortic wall. The wall may eventually stretch and then leak or burst. Smoking strongly contributes to aortic aneurysm formation. Smokers have an up to eight times greater risk of aortic aneurysm than non-smokers.