Prevention of heart disease
Significance of questions and answers
Assessment of an individual’s risk of developing coronary heart disease (CHD) involves the summation of both modifiable and non-modifiable risk factors for developing the disease. Non-modifiable risk factors include age, gender, ethnic origin and family history of coronary heart disease. These risk factors cannot be altered. Interventions to reduce absolute coronary heart disease risk are focused on modifiable risk factors.
Age and gender
With age the risk of developing coronary heart disease increases. Around 80% of people who die from heart disease are aged 65 years or over. It is commoner in men than in women. (The lifetime risk of developing it at age 40 years is one in two for a men and one in three for a women.) Postmenopausal women have a cardiovascular (CV) risk similar to that of men.
Ethnic origin
Heart disease in the UK is commoner in Afro-Caribbean people and those from the Asian subcontinent (Bangladesh, India, Pakistan and Sri Lanka).
Family history of coronary heart disease
Risk of developing coronary heart disease increases if an individual has a close relative (father, mother, brother or sister) with the disease. A family history of premature coronary heart disease (i.e. a father or brother who had a coronary event before the age of 55 years, or a mother or sister before the age of 65 years) is an even stronger indicator of risk.
Smoking history
Currently in the UK, 25% of men and 23% of women smoke. Smoking tobacco has been shown to increase the risk of MI. This effect is related to the number of cigarettes smoked; heavy smokers (more than 20 per day) increase their risk of MI by two- to fourfold over non-smokers. No level of smoking has been demonstrated to be safe. Those who have recently stopped smoking remain at a higher risk for as long as 5 years after stopping, but the risk begins to decline within a few months of stopping.
Waist circumference/body mass index
Obesity is associated with an increased risk of stroke, CHD, type 2 diabetes, hypertension and dyslipidaemia, i.e. raised total cholesterol (TC), high low-density lipoprotein (LDL) cholesterol and high triglyceride levels. Abdominal obesity (apple-shaped body) is particularly significant, and waist circumference may be a better predictor of susceptibility to coronary heart disease than body mass index. A waist circumference of more than 94 cm in men or 80 cm in women is associated with a relatively increased risk of CHD. Waist circumference may be a better way of assessing risk, especially in the Asian population compared to body mass index (BMI).
BMI is calculated by dividing an individual’s weight (kilogrammes) by height (metre) squared. The normal range of BMI is between 18.5 and 25 kg/m2. Overweight is defined as a BMI >25 kg/m2 and obesity is defined as a BMI >30 kg/m2.
Men in the UK increase their risk of CHD by 10% with every 1 kg/m2 increase in BMI above 22 kg/m2. Waist circumference >94 cm in men and 80 cm in women identifies a coronary heart disease risk equivalent to that of a BMI >25 kg/m2. For a circumference greater than 102 cm in men and 88 cm in women the risk is equivalent to that of a BMI >30 kg/m2.
About 47% of men and 33 % of women in the UK are overweight and an additional 23% of men and 24% of women are obese. Overweight and obesity increase with age. Overweight and obesity are increasing.
The percentage of adults who are obese has roughly doubled since the mid-1980s. Frequent fluctuations in weight are also associated with an increased risk of developing coronary heart disease.
Physical activity
Regular aerobic exercise has been proved to assist weight loss and reduce blood pressure. Physical inactivity is associated with an increased incidence of developing hypertension (a CHD risk factor).
Alcohol intake
Drinking more than 21 units of alcohol per week is associated with an increase in blood pressure, which can be reversed if the intake is reduced. Alcohol can affect most parts of the body and, in addition to causing liver damage, can cause infertility, skin damage, heart damage, cancer and strokes. Many accidents, episodes of violence and risk-taking behaviour, e.g. unprotected sex, are associated with alcohol. Excess alcohol in those under the age of 20 years can damage the brain while it is still developing. Small amounts of alcohol (such as one glass of red wine per day with a meal) may slightly reduce the chances of developing CHD. Safe drinking limits are 3-4 units per day for men and 2-3 units per day for women. Most experts advise at least two alcohol-free days each week.
Medical history (hypertension, diabetes and cholesterol/lipid profile)
Raised blood pressure (> 140/90 mm Hg) has been shown to be a risk factor for the development of stroke and CHD. Diastolic pressures of 90-109 mm Hg are found in about 20% of the middle-aged adult population. In younger people the prevalence is lower, and in elderly people it is higher. Current estimates suggest that in the UK around 40% of men and women have raised blood pressure. In addition, undertreated hypertension is common, with up to half of all people with diagnosed hypertension not reaching recommended targets.
Contributing factors to hypertension should be identified. These include obesity, excessive alcohol intake (3 units/day), high salt intake and physical inactivity.
Diabetes
Developing diabetes has the equivalent effect on increasing an individual’s coronary heart disease risk as having a heart attack. It increases CHD mortality by two to three times in men and four to six times in women. Eighty per cent of type 2 diabetics (the commonest type of diabetes, by a ratio of 9:1) are obese. This has led to the coining of the term ‘diabesity’, which cleverly combines the two conditions. Patients with type 2 diabetes have a two- to fourfold increased risk of, and a fourfold increase in, mortality from CHD. Intensive glycemic control has a more modest effect on reducing macrovascular than microvascular complications. This is because the development of cardiovascular disease (CVD) is multifactorial, and hyperglycaemia is only one of many risk factors.
Epidemiological data suggest that a glycosylated haemoglobin (HbAlc) level of 7% or less is reasonable to avoid or minimise the complications associated with type 2 diabetes. Studies have shown that there is an increased risk of cardiovascular mortality even before the onset of type 2 diabetes.
Many studies, including the Framingham Heart Study, have clearly established that high total cholesterol levels are associated with increased risk of developing coronary heart disease. CHD is caused when the blood vessels to the heart (the coronary arteries) become narrowed by a gradual build-up of fatty material within their walls – a condition called atherosclerosis. Atheroma develops when low-density lipoprotein cholesterol is oxidised and is taken up by cells in the coronary artery walls where the narrowing process begins. On the other hand, high-density lipoprotein (HDL) cholesterol removes cholesterol from the circulation and appears to protect against CHD. So the ratio of HDL to LDL is important. The goal is to have a low level of LDL (>3 mmol/L) and a high level of HDL (>1 mmol/L).
As a general rule, the higher the total cholesterol level, the greater is the risk to health. A total cholesterol level of less than 5 mmol/L is often a target aimed for. However, more than half of adults in the UK have a total cholesterol level above this figure. Increasing importance is being placed on LDL rather than total cholesterol; from long-term epidemiological studies and intervention studies with statins, it is clear that reductions in LDL levels correlate closely with reduction in coronary heart disease risk. This relationship (plotted on a logarithmic or doubling scale) is a straight line with no threshold below, which a reduction in low-density lipoprotein does not produce a further reduction in risk. This means that if someone has an absolute level of risk that justifies treatment, reducing the LDL will reduce that risk, whatever their starting level of cholesterol.
The level of low-density lipoprotein cholesterol in the blood tends to rise, and high-density lipoprotein falls, with the amount of saturated fat that is eaten. On the other hand, unsaturated fats have a good effect as they tend to lower LDL levels. A high level of triglycerides also increases the risk of CHD and stroke.
Medication
A full medication history is important as some medicines can affect CHD risk either positively or negatively. The potential contribution of over-the-counter (OTC) medicines should also be considered. Medications with a positive effect on coronary heart disease risk will be considered later in the chapter. Factors predisposing to CV toxicity include existing heart disease, uncorrected electrolyte abnormalities and poor renal function.
Sympathomimetic drugs such as adrenaline, noradrenaline, dobutamine, dopamine and phenylephrine can all cause systemic hypertension and precipitate heart failure. Other commonly prescribed medicines with CV side-effects include thyroxine, tricyclic antidepressants and triptans.
Sudden withdrawal of beta-blockers may induce unstable angina, MI and sudden death. This is thought to be due to an increased myocardial oxygen consumption caused by an increase in heart rate subsequent to the removal of beta-blockers. This effect is more commonly seen after short-acting beta-blockers are stopped.
Epidemiological studies have demonstrated that combined oral contraceptives increase the risk of CVD. Oral contraceptives have complex effects on blood pressure, platelet function, blood coagulation, carbohydrate metabolism and lipid metabolism. Similarly, current evidence suggests that hormone replacement therapy (HRT) should not be used for the prevention of coronary heart disease postmenopause.
Continuation: Managing heart disease risk in the pharmacy
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