Stroke is a significant healthcare burden recognized globally. According to the World Health Organization, by the year 2020, there will be an epidemic stroke. During the 2004 World Stroke Day Declaration, it was said that if nothing is done the predicted number of people who will have stroke will double by 2020 but if what is already known is applied, half of the number of strokes could be prevented.
Identification of risk factors for stroke, awareness of the relative importance of each risk factor and knowledge of their interaction should facilitate stroke prevention. The major atherogenic risk factors are hypertension, blood lipid levels, diabetes, obesity, family history, fibrinogen and other clotting factors, homocysteine and cardiac disorders.
Hypertension is the principal risk factor for transcerebral hemorrhage (ICH) and for ischemic stroke. It also predisposes to cardiac conditions notably myocardial infraction and atrial fibrillation. Hypertension also increases the risk for subarachnoid hemorrhage from cerebral aneurysms. Studies have shown a linear correlation of increasing BP for the occurrence of first stroke. The International Stroke Trial showed that both high and low blood pressures were independent prognostic factors for poor outcome. Early death increases by 17.9% for every 10mmHg drop from 150mmHg systolic and by 3.8% for every 10mmHg increase above 150mmHg systolic. The rate of recurrent ischemic stroke within 14 days increased by 4.2% for every 100mmHg increase in SBP. No relationship between symptomatic ICH and SBP was seen. Low SBP was associated with severe clinical stroke and excess of death from coronary heart disease.
With the increasing levels of total serum cholesterol, there is a steady increase in CHD. The incidence of CHD is directly related LDL and inversely related to HDL cholesterol levels. Stroke, generally has no clear or consistent relationship with blood lipid levels. The Atherosclerosis Risk in Communities Study (ARTC) showed a weak association between ischemic stroke and each of the five lipid factors. However, other studies like the Honolulu Heart Study of Hawaiian Men of Japanese Ancestry and in the Multiple Risk Factor Intervention Trial (MRFIT) showed a direct relationship between elevated cholesterol levels and incidence of ischemic strokes.
While there seems to be no definite association between blood lipids and ischemic strokes, a significant reduction in stroke incidence was seen in a series of trials that used statins. This trend was seen in the CARE trial, the LIPID trial, the Heart protection study and the ASCOT trial. It has been suggested that statins acted by altering the lipid composition of the plaque, thereby reducing the tendency to rupture of fissure, by diminishing the inflammation or by improving the hemorrheologic event.
Diabetic persons have a high susceptibility to atherosclerosis and up to 80% of those with DM type 2 will suffer from all ages in both men and women with glucose intolerance, the risk of ischemic strokes is approximately double that in a non diabetic persons. Furthermore, post stroke hyperglycemia leads to a greater risk for mortality and poorer outcome.
Much has to be learned regarding the interplay of the various risk factors for stroke. However, if we believe that stroke is preventable, then we must foster collaboration for research and public awareness in order to effect changes. Much has to be done but all efforts are worthwhile if we succeed in reducing the devastating consequences of stroke.