Age Age is the most powerful single stroke risk factor.
About 30% of strokes occur before the age of 65; 70%
occur in those 65 and over. The risk of stroke approxi-mately doubles for every decade of age over 55 years Hypertension The risk of stroke is related to the level of systolic hy-pertension. This applies to both sexes, all ages, and to the risk for hemorrhagic, atherothrombotic, and lacunar stroke. Interestingly, the risk of stroke at a given level of systolic hypertension is less with advanc-ing age, so that it becomes a less powerful, although still important and treatable, risk factor in the elderly Sex Brain infarcts and stroke occur about 30% more
frequently in men than women; the sex differential is even higher before age 65
Family history A fivefold increase in the prevalence of stroke among monozygotic compared to dizygotic male twin pairs suggests a genetic predisposition to stroke. The 1913 Swedish birth cohort study demonstrated a threefold increase in the incidence of stroke in men whose mothers died of stroke, compared with men without such a maternal history. Family history also seems to play a role in stroke mortality among the upper middle-class Caucasian population in California Diabetes mellitus After other stroke risk factors have been controlled
for, diabetes increases the risk of thromboembolic stroke by approximately twofold to threefold relative to persons without diabetes. Diabetes may predispose an individual to cerebral ischemia via acceleration of atherosclerosis of the large vessels, such as the coro-nary artery or carotid tree, or by local effects on the cerebral microcirculation
Cardiac disease Individuals with heart disease of any type have more than twice the risk of stroke compared to those with normal cardiac function
– Coronary artery
dis-ease Both a strong indicator of the presence of diffuse atherosclerotic vascular disease and a potential source of emboli from mural thrombi due to myocardial in-farction
– Congestive heart failure, hypertensive heart disease
Associated with increased stroke
Stroke Risk Factors
– Atrial fibrillation Strongly associated with embolic stroke and atrial fi-brillation due to rheumatic valvular disease; substan-tially increases the stroke risk by 17 times
– Other Various other cardiac lesions have been associated with stroke, such as mitral valve prolapse, patent fora-men ovale, atrial septal defect, atrial septal aneurysm, and atherosclerotic and thrombotic lesions of the as-cending aorta
Carotid bruits A carotid bruit does indicate an increased risk of a fu-ture stroke, although the risk is for stroke in general, and not for stroke specifically in the distribution of the artery with the bruit
Smoking Several reports, including a meta-analysis of a number of studies, have shown that cigarette smoking clearly confers an increased risk for stroke In all ages and both sexes; that the degree of risk correlates with the number of cigarettes smoked; and that cessation of smoking reduces the risk, with the risk reverting to that of nonsmokers by five years after cessation Increased hematocrit Heightened viscosity causes stroke symptoms when
hematocrit exceeds 55%. The major determinant of whole blood viscosity is the red blood cell content;
plasma proteins, particularly fibrinogen, play a con-tributing role. When heightened viscosity results from polycythemia, hyperfibrinogenemia, or paraproteine-mia, it usually causes generalized symptoms, such as headache, lethargy, tinnitus, and blurred vision. Focal cerebral infarction and retinal vein occlusion is much less common, and may follow platelet dysfunction due to thrombocytosis. Intracerebral and subarachnoid hemorrhages may occur occasionally
Elevated fibrinogen level and other clotting system abnormalities
An elevated fibrinogen level constitutes a risk factor for thrombotic stroke. Rare abnormalities of the blood clotting system have also been noted, such as anti-thrombin III deficiency, and deficiencies of protein C and protein S and are associated with venous throm-botic events
Hemoglobinopathy
– Sickle-cell disease Can cause ischemic or hemorrhagic infarction, in-tracerebral and subarachnoid hemorrhages, venous sinus and cortical vein thrombosis. The overall inci-dence of stroke in sickle-cell disease is 6 – 15%.
– Paroxysmal noc-turnal hemoglo-binuria
May result in cerebral venous thrombosis
Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme
157
Drug abuse Drugs that have been associated with stroke include methamphetamines, norepinephrine, LSD, heroin, and cocaine. Amphetamines induce a necrotizing vasculitis that may result in diffuse petechial hemorrhages, or focal areas of ischemia and infarction. Heroin can pro-duce an allergic vascular hypersensitivity leading to farction. Subarachnoid hemorrhage and cerebral in-farction have been reported after the use of cocaine Hyperlipidemia Although elevated cholesterol levels have been clearly
related to coronary heart disease, their relation to stroke is less clear. Elevated cholesterol does appear to be a risk factor for carotid atherosclerosis, especially in males under 55 years. The significance of hyper-cholesterolemia declines with increasing age.
Cholesterol below 160 is related to intracerebral hemorrhage or subarachnoid hemorrhage. There is no apparent relationship between cholesterol level and lacunar infarction
Oral contraceptives Early high-estrogen oral contraceptives were reported to increase the risk of stroke in young women. Reduc-ing the estrogen content has decreased this problem, but not eliminated it altogether. This risk factor is strongest in women over 35 years who are also smokers. The presumed mechanism is increased coagulation, due to estrogen stimulation of liver pro-tein production, or rarely an autoimmune cause Diet
Alcohol consumption There is an increased risk of cerebral infarction, and subarachnoid hemorrhage has been associated with alcohol abuse in young adults. Mechanisms by which ethanol can produce stroke include effects on blood pressure, platelets, plasma osmolality, hematocrit, and red blood cells. In addition, alcohol can induce myocardiopathy, arrhythmias, and changes in cerebral blood flow and autoregulation
Obesity Measured using relative weight or the body mass index, obesity has consistently predicted subsequent strokes. Its association with stroke could be explained partly by the presence of hypertension and diabetes.
A relative weight more than 30% above average was an independent contributor to a subsequent athero-sclerotic brain infarction
Peripheral vascular dis-ease
Stroke Risk Factors
Infection Meningeal infection can result in cerebral infarction through the development of inflammatory changes in vessel walls. Meningovascular syphilis and mucormy-cosis can cause cerebral arteritis and infarction Homocystinemia or
homocystinuria (homo-zygous form)
Predisposes to cerebral arterial or venous thromboses.
The estimated risk of stroke at a young age is 10 – 16%
Migraine
Ethnic group African-Americans have disproportionately higher rates of stroke than other groups
Geographic location In the United States and most European countries, stroke is the third most frequent cause of death, after heart disease and cancer. Most often, strokes are caused by atherosclerotic changes rather than by hemorrhage. An exception is middle-aged black women, in whom hemorrhage tops the list. In Japan, stroke is the leading cause of death in adults, and hemorrhage is more common than atherosclerosis Circadian and seasonal
factors The circadian variation of ischemic strokes, peaking between 10 a.m. and noon, has led to the hypothesis that diurnal changes in platelet function and fibrinoly-sis may be relevant to stroke. A relationship between seasonal climatic variation and ischemic stroke occur-rence has been postulated. An increase in referrals for cerebral infarction was observed during the warmer months in Iowa. The mean ambient temperature showed a negative correlation with the incidence of cerebral infarction in Japan. Seasonal temperature var-iation has been correlated with a higher risk of cere-bral infarction in 40 – 64-year-olds who are nonhyper-tensive, and in individuals with a serum cholesterol below 160 mg/dL
LSD: lysergic acid diethylamide.
Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme