Epidemiology and Risk Factors

Figure 5-1

Ischemic stroke subtypes

Embolic: 20 %
Large vessel (thrombotic): 20 %
Small vessel: 25 %
Cryptogenic: 30 %

Hemorrhagic stroke: 20 % of all strokes

Risk of early stroke recurrence: large artery > cardioembolic > lacunar > cryptogenic

Functional Outcomes

Lacunar strokes associated with best functional outcomes, survival rates, and lowest risk of recurrence (compared to large artery or cardioembolic) (Fig. 5-2)

Figure 5-2

Risk of stroke recurrence Petty et al. Stroke, 2000 may
Cardioembolic strokes associated with worst outcomes, highest rates of death

Nonmodifiable Risk Factors

Age: strongest determinant of stroke risk
Gender: men in general are at higher risk stroke than women
- Women have a higher rate of stroke later in life compared to men (because women live longer)
- Aspirin 81 mg is useful in primary stroke prevention in women, particularly those with diabetes mellitus
Race
- Risk of first time stroke: African Americans, Hispanics > whites
- Extracranial disease: whites > African Americans
- Intracranial disease: African Americans, Chinese > whites
Genetic Factors
- Framingham study: parental history of stroke before age 65 associated with threefold increase in risk of stroke in offspring
- Several monogenic disorders are associated with stroke (discussed in detail later)
- Genetic counseling should be considered for patients with genetic causes of stroke or known family history of hereditary disease

Modifiable Risk Factors

Hypertension : most important modifiable risk factor in ischemic and hemorrhagic stroke
- Defined as 140/90
- Pre-hypertension : 120–139/80–89: lifestyle changes recommended
- African Americans > whites
- Prevalence: at least 30 % of adults of all ages in the USA (>140/90)
- Individuals normotensive at age 55 have 90 % lifetime risk for developing HTN
- Linear relationship between blood pressure and stroke risk; every 10 mmHg reduction in BP = 33 % lowering of stroke risk
Cardiac Disease
- Atrial Fibrillation (AF): fivefold increase in stroke risk
  
  Prevalence: 2.7 m Americans
  
  Caucasians > African Americans
  
  9 % of people > 65 years or older have AF
  
  Increased risk of developing AF with age, and incidence of AF- related stroke expected to increase in coming years due to aging population
  
  Most frequent cause of cardioembolic (CE) stroke, accounts for approximately 50 % of all CE strokes
Congestive Heart Failure: fourfold increased risk of stroke
- See WATCH and WARCEF trials below
Coronary Artery Disease: twofold increased risk of stroke
Chronic Kidney Disease
Peripheral Arterial Disease

Notable Trials

WATCH (2009): Randomized controlled trial comparing outcomes in patients with heart failure and Ejection Fraction (EF) ≤ 35 % and no history of atrial fibrillation to determine best medical therapy for prevention of primary endpoints of death, nonfatal myocardial infarction or stroke. Patients were randomized to open-label warfarin (INR 2.5–3) versus blinded aspirin 162 mg versus blinded clopidogrel 75 mg. The study terminated early due to poor enrollment. Warfarin had a lower incidence of stroke compared to antiplatelet agents but higher risk of bleeding; warfarin was not superior to antiplatelet therapy, and treatment with clopidogrel was not superior to aspirin. It also found increase in hospitalization for worsening heart failure in the aspirin group (Massie et al. 2009).

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