Hypertension is the single most important modifiable risk factor for ischemic stroke. Most estimates for hypertension indicate a relative risk of stroke of approximately 4 when hypertension is defined as systolic blood pressure ≥160 mm Hg and/or diastolic blood pressure ≥95 mm Hg. A summary of seven studies assigning a relative risk of 1 for borderline or mild hypertension determined the relative risk to be about 0.5 at a blood pressure of 136/84 mm Hg and about 0.35 at a blood pressure of 123/76 mm Hg.91
Treatment was also highly effective in preventing stroke in elderly persons with isolated systolic hypertension (Systolic Hypertension in the Elderly Program [SHEP]), the most prevalent form of hypertension in persons older than 65years . Importantly, there was no less impact on stroke prevention above age 80, with incidence reduced by 40%. 92Alkali found that 82 % of stroke cases were hypertensive .54
DIABETES AND GLUCOSE METABOLISM
Persons with diabetes have an increased susceptibility to atherosclerosis and an increased prevalence of atherogenic risk factors, notably hypertension, obesity, and abnormal blood lipids.93 Ekeh et al observed that diabetes mellitus was the predominant stroke risk factor in 31% of stroke admissions .93
DYSLIPIDEMIA
Dyslipidemia is a known modifiable risk factor for stroke.Available, data clearly support the positive relation between total and LDL cholesterol and a protective influence of HDL cholesterol on extracranial carotid atherosclerosis.)In secondary analyses, the Scandinavian Simvastatin Survival Study (4S) found a reduction of fatal or nonfatal stroke with
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simvastatin versus placebo (RR=.70, 95% confidence interval .52, .96), and the Asymptomatic Carotid Artery Plaque Study (ACAPS) reported fewer strokes in the lovastatin versus placebo group (5 versus 0). 94
However, Ogunrin did not find any difference in the serum lipids of Nigerian patients with stroke with the exception of serum triglyceride, which seemed to confer significant stroke risk. 95
CIGARETTE SMOKING
Cigarette smoking increases risk (RR) of ischemic stroke nearly two times,96 with a clear dose-response relation. In both the Framingham Study and the Nurses’ Health Study cessation of smoking led to a prompt reduction in stroke risk—major risk was reduced within 2 to 4 years. This reduction in risk occurred throughout the age spans of these studies and in heavy as well as moderate smokers. Smoking has also been identified as a major risk factor for stroke, accounting for about 6.8% of stroke cases .97,98
ALCOHOL
Moderate consumption of alcohol may reduce cardiovascular disease, including stroke.
Recent epidemiological studies have shown a U-shaped curve for alcohol consumption and coronary heart disease mortality, with low to moderate alcohol consumption associated with lower overall mortality. 99
Gill observed that low levels of alcohol consumption had a protective effect upon the cerebral vasculature, whereas heavy consumption predisposes to both hemorrhagic and non-hemorrhagic stroke.100
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LIFESTYLE FACTORS (OBESITY, PHYSICAL ACTIVITY, DIET, AND ACUTE TRIGGERS)
Various lifestyle factors have been associated with increased stroke risk. These include obesity, physical inactivity, diet, and acute triggers such as emotional stress. Obesity has been associated with higher levels of blood pressure, blood glucose, and athero-genic serum lipids, which are independent risk factors for stroke.101
In Framingham, obesity defined as a Metropolitan Life chart relative weight greater than 30% above average was a significant independent contributor to incidence of brain infarction in men aged 35 to 64 and women aged 65 to 94.102I
The PREDIMED Study (PREvención con DIeta MEDiterránea), a multicenter, randomized, controlled, clinical trial which involved 7,216 men and women at high cardiovascular risk, aged 55 to 80 years, Olive oil consumption, specifically the extra-virgin variety, is associated with reduced risks of cardiovascular disease and mortality in individuals at high cardiovascular risk..103
A recent study conducted in 2015 revealed that while high Mediterranean diet consumption protected against ischemic stroke , it was not found to protect against hemorrhagic strokes.104
HEMOSTATIC AND INFLAMMATORY FACTORS
Haemostatic factors have been related to incidence of cardiovascular disease generally, and in two prospective studies fibrinogen has been linked to increased stroke risk. In Goteborg, there was an independent graded relationship between fibrinogen levels and incidence of
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stroke in 54-year-old men.105 The Framingham Study confirmed these observations in men, but among women the relation did not reach statistical significance.106
Fibrinogen has also been prospectively linked to both progression of carotid artery stenosis and risk of recurrent stroke. The mechanisms by which fibrinogen may be related to stroke risk include effects on viscosity, platelets, and atherogenesis, as well as its direct role in clot formation as the substrate for thrombin.107
HOMOCYSTEINE
Blood levels of homocysteine, produced from the essential amino acid methionine, can be determined by genetic factors and by intake of vitamins B6, B12, and folic acid. Numerous case-control studies have shown a strong relation between stroke and both basal and post-methionine load moderate hyper-homo-cysteinemia. The British Regional Heart Study showed a strong, independent, and graded relation of homocysteine level to stroke risk among middle-aged men.108
CARDIAC DISEASE
Various cardiac diseases have been shown to increase risk of stroke. Atrial fibrillation (AF) is the most powerful and treatable cardiac precursor of stroke. The incidence and prevalence of AF increases with age. With each successive decade of life above age 55, incidence of AF doubles. the elderly are particularly vulnerable to stroke when atrial fibrillation is present.109A study Barletta suggested that in young people cerebral ischemic events could be
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related to the presence of a combined valve prolapse and to an echocardiographic picture of valve diffuse thickening.110
2.5 PROGNOSTIC FACTORS IN ISCHEMIC STROKE