Prevention of stroke
Executive Editor, InnovAiT
E-mail: chantal.simon{at}oxfordjournals.org
In England alone, over 100 000 people a year have a stroke. Three-quarters of them are over the age of 65 years. More than one in five of those individuals will die in the period immediately after their stroke. The survivors return to the community and every practice in the UK has a median prevalence of 14.7 patients who have had a stroke or transient ischaemic attack (TIA) per 1000 patients registered (Fig. 1). Ninety per cent of those who survive will be left with some permanent disability as a result of their stroke, making stroke the most common cause of adult onset disability, and costing the nation more than £ 7 billion every year. This figure is set to rise as the population of the UK ages and people survive in a disabled state for longer.
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Patients with a history of stroke or transient ischaemic attack have a 30–43% risk of recurrent stroke within 5 years. Prevention of stroke focuses on prevention of ischaemic and embolic events which account for the majority of strokes. It is cost effective and a key element of the Quality and Outcomes Framework (QOF) in primary care.
Primary care management A GP must be able to provide appropriate chronic disease management including stroke prevention and describe strategies for the early detection of cardiovascular problems that may already be present but have not yet produced symptoms.
Knowledge base
Person-centred care
Contextual aspects
Attitudinal aspects
Scientific aspects
Psychomotor skills
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Organization of preventive care |
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The vast majority of both primary and secondary stroke prevention work occurs in nurse-led clinics—for example cardiovascular disease, hypertension or diabetic clinics. GPs should be involved with organization of care, help develop the structure of reviews, be available to manage problems that are found during the course of reviews and manage medication. Use of templates ensures that patients receive comprehensive care and that all the data required for the QOF are recorded.
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Lifestyle measures |
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Lifestyle measures are important for both primary and secondary prevention of cardiovascular diseases of all types.
Smoking
All patients should be discouraged from smoking, and particularly those who have had any sort of episode of cardiovascular disease. The risk of stroke increases with the number of cigarettes smoked so that heavy smokers, smoking more than 40 cigarettes per day, have twice the risk of light smokers, smoking less than 10 cigarettes per day. Smoking cessation lowers the risk of stroke significantly within 2 years after stopping, and the risk reaches the level of a non-smoker at 5 years.
The QOF rewards practices for gathering data on smoking and offering smokers advice on cessation (Table 1). Advice from a GP about smoking cessation results in 2% of smokers stopping—5% if advice is repeated. Strong motivation, often secondary to an episode of poor health directly related to smoking, such as a stroke, is a vital factor. In many areas ‘stop smoking’ services are provided by Primary Care Organizations. These programmes vary from area to area but generally consist of group education, counselling and support, in combination with drug therapy. Drug therapy increases smoking cessation rates by 1.5 to 2 times, whether nicotine replacement, bupropion or varenicline is used.
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Diet and obesity
Obesity is one of the most important preventable diseases in the UK. The best measure of obesity is body mass index (BMI). The QOF rewards practices for keeping a register of patients with BMI of more than 30 kg/m2 (Obesity 1). Waist circumference is an alternative, indirect, measurement of body fat that reflects the intra-abdominal fat mass. It is strongly correlated with risk of first and recurrent stroke, diabetes, hyperlipidaemia and hypertension. It is measured halfway between the superior iliac crest and the rib cage in the mid-axillary line (Table 2). This may be a better measurement of stroke risk than BMI.
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Treatment of obesity is a complex issue. In general, individuals should aim for a BMI of not more than 25 kg/m2. This can be achieved by a combination of decreased energy intake (diet) and increased energy expenditure (more exercise) and may necessitate drug treatment with drugs that reduce fat absorption from the gut such as Orlistat, or central appetite suppressants such as sibutramine or rimonabant, or even surgery.
A good diet should be low in fat and salt, high in fibre and include plant sterols. Salt ingestion is a major risk factor for stroke. Average salt intake in the UK is about 9.5 g/day, more than twice the amount needed. The major impact of salt is through its effect on blood pressure. Even a modest decrease of salt intake of 3 g/day (less than half a teaspoon) drops risk of stroke by around 13% (Table 3). Advise patients to:
- Cut down on salty foods, such as crisps, nuts, salted meats (e.g. bacon and gammon), salty sauces (e.g. soy sauce) and stock cubes.
- Use less salt in cooking and not add salt to food. Flavouring food with herbs and spices is an alternative.
- Read food labels. Approximately 75–80% of our salt intake comes from salt added to processed foods. Choose foods with lower sodium levels—0.1 g per 100 g is low; 0.5 g per 100 g or more is high.
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Alcohol
Recommended safe levels of alcohol consumption are 21 units per week for men and 14 units per week for women. A recent meta-analysis of alcohol as a risk factor for stroke showed that, compared to abstainers, those drinking more than 7.5 units (60 g) of alcohol per day have a relative risk of total stroke of 1.64 (relative risk of ischaemic stroke is 1.69 and relative risk of haemorrhagic stroke is 2.18). However, consumption of lesser amounts of alcohol may be protective against ischaemic but not haemorrhagic stroke (relative risk of ischaemic stroke is 0.83 for those consuming less than 1.5 units of alcohol per day, and 0.72 for those drinking 1.5–3 units of alcohol per day).
Exercise
Exercise is beneficial to many aspects of health, in particular cardiovascular health. Physical activity has been shown to reduce both stroke incidence and mortality. Highly active individuals have a 21% lower risk of ischaemic stroke and a 34% reduced risk of haemorrhagic stroke compared to less active individuals.
This effect is probably mediated through a variety of mechanisms. There may be a direct effect, but exercise also reduces obesity, hypertension, hypercholesterolaemia and improves insulin sensitivity thus reducing the risk of diabetes. These are all risk factors for stroke. It is recommended that adults take at least 30 minutes of moderate-intensity exercise (e.g. brisk walking) on at least 5 days every week and that children take at least an hour of moderate-intensity activity every day.
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Antiplatelet drugs |
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Primary prevention
Aspirin is used for primary and secondary prevention of stroke. For primary prevention, advise patients over 50 years of age who have a 10-year cardiovascular disease risk of 20% or more to take 75 mg of aspirin each day. Aspirin reduces the long-term risk of stroke by about a quarter at a cost of a small increase in risk of bleeding. Consider prescribing gastric prevention together with aspirin, for example with a proton pump inhibitor such as omeprazole, for elderly patients or those with a history of gastric symptoms.
For patients with diabetes mellitus who do not have cardiovascular disease, recommend 75 mg of aspirin per day from the patient's 50th birthday or if the patient is younger but has had diabetes for more than 10 years. Patients with hypertension should start aspirin 75 mg daily once their blood pressure is controlled to less than 150/90, if they are 50 years of age or older, diabetic, have target organ damage (left ventricular hypertrophy, renal impairment, retinal vein occlusion, transient ischaemic attack or stroke, myocardial infarct or angina) or have a 10-year cardiovascular risk of more than 0%.
Secondary prevention
All patients not taking warfarin, who have suffered a non-haemorrhagic stroke (confirmed on CT or MRI scan) or a TIA should be started on aspirin as soon as possible after the event. However, patients with suspected stroke in the community, should not start aspirin prior to admission. For secondary prevention, aspirin reduces long-term risks of cardiovascular events by about a quarter. The standard dose of aspirin for maintenance therapy is 75 mg daily. Clopidogrel 75 mg daily is an expensive alternative for patients intolerant to aspirin. There is currently no robust evidence that combining aspirin with clopidogrel reduces stroke risk further. For patients at high risk of recurrence, or who have further events while taking aspirin, there is evidence that combining aspirin with dipyridamole 200 mg b.d. is beneficial.
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Warfarin |
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Primary prevention
Patients who have identified potential causes of cardiac thromboemboli should be anticoagulated with warfarin. This includes patients with:
- Rheumatic mitral valve disease
- A prosthetic heart valve
- Dilated cardiomyopathy and
- Atrial fibrillation (AF) associated with valvular heart disease or prosthesis.
If a patient in AF is aged less than 65 years and has no additional risk factors for stroke (i.e. risk of stroke is less than 3%), give aspirin 75–300 mg daily as stroke prophylaxis. If a patient in AF is aged 65 years or more, or has one or more additional risk factors for stroke, consider anticoagulation with warfarin (maintaining the INR between 2 and 3) in preference to aspirin. Up to 15 QOF points are available for practices which ensure that all their patients in AF are on warfarin, aspirin or equivalent, with an attainment range of 40–90% (AF indicator 3).
Weigh the risks of prescribing warfarin against the benefits (Table 4), taking the patient's wishes, mental and physical health and social circumstances into consideration. Risk of serious gastrointestinal bleeding in patients taking warfarin is approximately nine per thousand patients per year. In addition, there is the inconvenience to the patient of having to have regular blood tests for warfarin monitoring. Stroke risks are cumulative, so if there is more than one additional risk factor (such as diabetes and hypertension), then benefits of anticoagulation increase.
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Secondary prevention
All patients who have suffered a stroke or TIA and have persistent or paroxysmal AF or a major source of cardiac embolism should be anticoagulated with warfarin unless there are clear contraindications. Anticoagulants decrease the risk of recurrent stroke by two-thirds (odds ratio 0.36) and the risk of all vascular events by a half (odds ratio 0.55) at the cost of an increased risk of extra- but not intracranial haemorrhage. Treatment should be started more than 2 weeks after the stroke and only if haemorrhagic stroke has been excluded. The target INR is 2–3 if the patient has no other indication.
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Hypertension management |
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About half of the British population aged between 65 and 74 years have hypertension. Raised blood pressure is symptomless until it causes organ damage, such as stroke. Systolic and diastolic blood pressure independently predict stroke. Risk escalates with increasing blood pressure. Primary prevention aims to detect and treat hypertension before damage occurs. Secondary prevention aims to control blood pressure to reduce risk of recurrence of stroke. The principles of treatment are the same for both. A 5–6 mmHg reduction in blood pressure reduces stroke risk by more than 30%.
There is no figure above which hypertension can be diagnosed definitively, although currently treatment is considered at once blood pressure exceeds 140/90. After stroke (but not after TIA) defer treating hypertension until more than 2 weeks after the event as hypertension may be a physiological response. Lowering blood pressure in those cases decreases perfusion of the brain and may be harmful.
Aims of treatment are to lower blood pressure to below 140/85 (and below 130/80 if the patient is diabetic). Benefits of treatment remain in patients up to 85 years of age—and probably beyond. Patients over 80 years of age should be offered the same treatment as younger patients, taking into account any co-morbidity and existing drug use.
All hypertensive patients should be offered advice about non-pharmacological treatment. Measures include decreasing salt intake, decreasing alcohol intake and increasing exercise, as well as losing weight. Such measures help with lowering blood pressure but are generally not enough: pharmacological intervention is nearly always necessary. The two major guideline-producing bodies in the UK have now combined to produce consensus guidelines for the treatment of hypertension in primary care (Fig. 2). The National Stroke Guidelines recommend treatment of patients who have already had a stroke or TIA with a combination of a thiazide diuretic and ACE inhibitor.
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Regular review of patients with hypertension is essential. Once raised blood pressure is controlled, routine review can be undertaken by properly trained practice nurses but annual review of medication should be undertaken by a GP, and the GP must review if the blood pressure is not controlled.
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Cholesterol |
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Blood cholesterol concentration is not steady over time. A quarter of raised serum cholesterol tests are normal on repeat testing. Therefore, it is important to check at least two samples at different times before diagnosing that a patient has high cholesterol. Before initiating treatment or if screening for familial dyslipidaemia, take fasting samples, and check triglyceride levels as well. For screening and routine follow-up, take non-fasting samples, testing total blood cholesterol and total cholesterol : HDL ratio. All those who have proven cardiovascular disease should have cholesterol levels checked annually.
All patients should be offered non-pharmacological advice on lifestyle factors that influence lipid levels. Generally, dietary fat should be kept to 30% or less of total energy intake. Advise patients to eat a low-cholesterol diet, increase fruit and vegetables and decrease salt intake. In patients with a BMI 30 kg/m2 or more, weight loss of 10 kg results in a 7% decrease in LDL and a 13% increase in HDL cholesterol. Increase in or more, physical activity also enhances cholesterol-lowering effects of diet and weight loss. At the same time, give general advice about lowering cardiovascular risk, for example smoking cessation.
Primary prevention
The concept of overall risk is important when making decisions about whether to treat patients with drugs to prevent cardiovascular events. Analysis of data from the coronary prevention trials shows that a 22% decrease in cholesterol produces a 30% reduction in stroke in individuals with no history of stroke or TIA.
For non-diabetic patients, treat with a statin, such as simvastatin 40 mg nocte, if the patient has a 10-year cardiovascular disease 20% or more and the total cholesterol is more than 4 mmol/l or LDL cholesterol is more than 2 mmol/l. For diabetic patients, initiate statin treatment if the patient is 40 years of age or older is aged 18–39 years but has one or more other cardiovascular risk factors, such as retinopathy or family history of premature cardiovascular disease.
Cardiovascular risk is often calculated automatically by in-practice computer systems, or can be estimated with tables, such as those available in the British National Formulary, or special computer programmes, such as the coronary heart disease event and stroke risk calculator (download free from the British Hypertension Society website: www.bhsoc.org).
Secondary prevention
There is evidence to suggest that all patients with a history of cardiovascular disease should be treated with a statin regardless of baseline cholesterol. National Stroke Guidelines suggest treatment with a statin if a patient is diabetic or total cholesterol is greater than 3.5 mmol/l unless statins are contraindicated.
Treatment target
In all, cases aim to decrease total cholesterol by 25% or to less than 4 mmol/l—whichever is the lower value, or to decrease LDL cholesterol by 30% or to less than 2.0 mmol/l—whichever is the lower value.
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Diabetes mellitus |
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Diabetes is a major risk factor for stroke, especially among those under the age of 55 years. Diabetes is present in 15% of patients presenting with stroke, and up to a third of those presenting with stroke aged under 55 years. Diabetics are at two to five times increased risk of myocardial infarction, compared to the general population. Furthermore, diabetics with the metabolic syndrome, consisting of insulin resistance, dyslipidaemia and central obesity, have an even higher risk of all types of cardiovascular disease and need to be treated aggressively.
Blood glucose levels should be kept as low as possible, with a target HbA1c of less than 7.5%. For those diabetics with higher risk of arterial disease due to other risk factors, HbA1c should be kept less than 6.5%. BP should be lowered if it is elevated above 140/85 with a target figure of 130/80 and hyperlipidaemia should be treated. Give aspirin at a dose of 75 mg/day to all diabetics:
- with evidence of vascular disease and/or
- if the patient is over 50 years of age, and/or
- if the patient has a history of diabetes for more than 10 years and/or
- if the patient is receiving treatment for hypertension.
There is some evidence that treatment of diabetes with glitazones (and in particular pioglitazone) may reduce recurrent, but not first, stroke. However, as yet, this is not standard treatment for secondary prevention of stroke in diabetes.
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Carotid stenosis and carotid endarterectomy |
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TOPThe GP curriculum and...Organization of preventive careLifestyle measuresAntiplatelet drugsWarfarinHypertension managementCholesterolDiabetes mellitusCarotid stenosis and carotid...VaccinationPatient self-helpReferences |
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Carotid endarterectomy reduces mortality from stroke if carotid stenosis (Fig. 3) is symptomatic. Benefits decrease as the degree of stenosis gets smaller, and there is no evidence of benefit if a patient has less than 30% stenosis.
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Patients with asymptomatic stenosis
There is a 2% annual risk of stroke for patients with asymptomatic carotid stenosis, so the place of surgery is controversial. In general, risks outweigh benefits, so start aspirin and reduce other modifiable risk factors.
Patients with a history of stroke or TIA
Referral for carotid endarterectomy or carotid artery stenting should be considered for any patients who:
- have a history of stroke or TIA
- have more than 70% carotid artery stenosis and
- do not have severe disability.
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Vaccination |
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Patients disabled due to stroke are at risk from pneumococcal infection and influenza. Make sure that they are offered vaccination. Pneumococcal vaccination and annual influenza vaccination may be offered by practices to patients as a directed enhanced service. Up to 2 QOF points are available for giving annual influenza vaccination to patients who have had a stroke.
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Patient self-help |
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Whether for primary or secondary prevention, provision of information to patients can enable them to self-care and follow a healthier lifestyle. Box 1 lists some useful information resources for patients.
Box 1. Self-help information for patients
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Key points
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References |
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TOPThe GP curriculum and...Organization of preventive careLifestyle measuresAntiplatelet drugsWarfarinHypertension managementCholesterolDiabetes mellitusCarotid stenosis and carotid...VaccinationPatient self-helpReferences |
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Aguilar M, Hart R. Antiplatelet therapy for preventing stroke in patients with non-valvular atrial fibrillation and no previous history of stroke or transient ischemic attacks. Cochrane Database of Systematic Reviews (2000) (Issue 1):CD001925. DOI: 10.1002/14651858.CD001925.pub2.
Aguilar MI, Hart R. Oral anticoagulants for preventing stroke in patients with non-valvular atrial fibrillation and no previous history of stroke or transient ischemic attacks. Cochrane Database of Systematic Reviews (2000) (Issue 1):CD001927. DOI: 10.1002/14651858.CD001927.pub2.
Bandolier Salt intake: the lower the better. Available from: www.jr2.ox.ac.uk/bandolier/booth/hliving/saltbp.html [date last accessed 10.02.08].
Brunner EJ, Thorogood M, Rees K, et al. Dietary advice for reducing cardiovascular risk. Cochrane Database of Systematic Reviews (2005) (Issue 4):CD002128. DOI: 10.1002/14651858.CD002128.pub2.
Cina CS, Clase CM, Haynes RB. Carotid endarterectomy for symptomatic carotid stenosis. Cochrane Database of Systematic Reviews (1999) (Issue 3):CD001081. DOI: 10.1002/14651858.CD001081.
De Schryver ELLM, Algra A, van Gijn J. Dipyridamole for preventing stroke and other vascular events in patients with vascular disease. Cochrane Database of Systematic Reviews (2003) (Issue 1):CD001820. DOI: 10.1002/14651858.CD001820.pub3.
Dunn N, Everitt H, Simon C. Oxford general practice library: cardiovascular problems (2007) Oxford: Oxford University Press.
He FJ, MacGregor A. How far should salt intake be reduced? Hypertension (2003) 42:1093–1099.
JBS2. Joint British Society guidelines on prevention of cardiovascular disease in clinical practice. Heart (2005) 91(suppl_5):1–52.
Lee CD, Folsom AR, Blair SN. Physical activity and stroke risk: a meta-analysis. Stroke (2003) 34:2475–2482.
NICE. Website: www.nice.org.uk.
NICE. Nicotine replacement therapy & bupropion for smoking cessation (2002) Available from: www.nice.org.uk/guidance/index.jsp?action=byID&o=11452 [date last accessed 10.02.08].
NICE. Atrial fibrillation: the management of atrial fibrillation (2006) Available from: Available from: www.nice.org.uk/guidance/index.jsp?action=byID&r=true&o=10982 [date last accessed 10.02.08].
NICE. Brief interventions and referral for smoking cessation in primary care and other settings (2006) Available from: www.nice.org.uk/guidance/index.jsp?action=byID&r=true&o=11375 [date last accessed 10.02.08].
NICE. Obesity: the prevention, identification, assessment and management of overweight and obesity in adults and children (2006) Available from: www.nice.org.uk/guidance/index.jsp?action=byID&r=true&o=10999 [date last accessed 10.02.08].
NICE. Guidance on prescribing of varenicline (2007) Available from: www.nice.org.uk/guidance/index.jsp?action=byID&o=11809[date last accessed 10.02.08].
QResearch Quality of Care for stroke and TIA in general practice using the new GMS contract indicators (2005) National Audit Office. Available from: www.nao.org.uk/publications/nao_reports/05-06/0506452_GP_activity.pdf [date last accessed 10.02.08].
Reynolds K, Lewis B, Nolen JD, et al. Alcohol consumption and stroke: a meta-analysis. JAMA (2003) 289:579–588.
Royal College of Physicians. National clinical guidelines for stroke (2004) 2nd edition. Available from: www.rcplondon.ac.uk/pubs/books/stroke/index.htm [date last accessed 10.02.08].
Royal College of Physicians. Primary care concise guidelines for stroke (2004) Available from: www.rcplondon.ac.uk/pubs/books/stroke/stroke_primarycare_2ed.pdf [date last accessed 10.02.08].
Saxena R, Koudstaal PJ. Anticoagulants for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischaemic attack. Cochrane Database of Systematic Reviews (1995) (Issue 2):CD000185. DOI: 10.1002/14651858.CD000185.pub2.
Scottish Intercollegiate Guidelines Network (SIGN). Risk estimation and the prevention of cardiovascular disease (2007) Vol. 97. Available from: www.sign.ac.uk/pdf/sign97.pdf [date last accessed 10.02.08].
Simon C. Oxford general practice library: neurology (2006) Oxford: Oxford University Press.
Wolf PA, D'Agostino RB, Kannel WB, et al. Cigarette smoking as a risk factor for stroke. The Framingham Study. JAMA (1988) 259:1025–1029.
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